S.,
First, I feel great empathy for any mom experiencing a challenge that is just...so not pretty! A challenge that I'm assuming may also feel embarrassing for you. I applaud your seeking a range of opinions on this concern - it demonstrates (at least to me) you have a deep love of your child and the ability to look at things that may not be 'pretty' - things that may be hard for you - but, from your inquiry, my guess is you're up to the challenge.
If you ask me, there is no greater quality in a parent than someone willing to shed any guilt or personal emotion they may have in the situation, in an effort to see things from other angles, on behalf of doing the best job they can, in raising their child (to be a happily functioning member of society).
Whether we work or stay home (or a combination of both), this is one of the most critical qualities that sets great parents apart from those who don't want to "deal" - those who let problems grow into lifelong hurdles for their offspring to deal with in their adult lives. In my view, great parents take challenges like this on as THEIR responsibility in teaching now, so that their children, as adults, can focus on successful activities and forward momentum for their future. So I have to say again - I totally applaud you for opening up a difficult subject - it speaks to your strengths as a parent.
I do not want to offend you in offering my two cents - but I AM going to be blunt because I believe this is a critical opportunity you have, to help your son in learning to better manage his social relationships - a skill I'm sure we agree he'll need to rely on for the overall success of his entire life.
Note, I am responding with the assumption that your writing above may leave out important details about your concerns and thoughts as a mom - basically, I'm responding ONLY to what I see written above - so take it or leave it with this in mind.
I sincerely hope this behavior will not get passed off on the "sensitivity" of a little girl - because that kind of comment has no place in ANY exchange between friends (or enemies!), be it between 7-year-olds or adults, for that matter.
The fact is, if anyone gave that retort in our adult world, it would be deemed totally inappropriate and cause others to walk away / end relations. It IS a socially repulsive behavior. I believe it is our job, as parents, to school our children in what is / is not socially acceptable. Plainly, if they are able to function in a positive way, socially, they are likely going to have FAR greater success in their lifetimes than if they are not.
In my view, your son is clearly in the wrong - no matter how sensitive the girl - no matter how provocative the situation seemed to be for your son.
The simple fact is, his behavior was socially way out of line and, if I were the mom, I would ensure that this singular message was the beginning, middle and end of the story told to my son. The girl has nothing to do with HIS choices. For his sake, he needs to learn to take TOTAL responsibility for his actions in life (as we all do - that's my opinion, at least), in order to have a happy and prosperous life.
Take it or leave it, but I say the ONLY focus for the well-being and happy future of your son (and those he socializes with in his lifetime) is HIS behavior. It's better he learn now, in the context of a loving family (what is going to help / hinder him in life), than when he leaves home for a world that doesn't share the same tolerance and affection for him (as we know the real world can be a great teacher!).
If it were my child, I would come up with a plan of action that looked something like this:
1) I would clarify to my son the nature of his behavior - that it is the only focus here and that, not only is it totally unacceptable, but it has real consequences. This is a rule that goes for me, as a mom, just as it goes for any child, including him. In this case, because HE CHOSE the behavior he did, the consequence is loss of a social relationship; they are not able to play together at this point and it has nothing to do with the parents or the little girl, for that matter. It is purely the result of his actions - basically, how we treat others brings consequences. Now, we can work to fix things - but that isn't a guarantee for success. The only guarantee for success is to fix our selves. He can make new and better choices, just as others can. On that note...
2) I would practice the art of a really decent and meaningful apology - and have my son practice with me. I would then approach the parents of the little girl. I would share with them what I have clarified to my son. That I have explained, in no uncertain terms, that this situation has NOTHING to do with their daughter - that it was his poor choice in behavior that has hurt her and caused them to not be able to play right now. I would underscore how truly invested I am, as a responsible parent, in his gaining personal growth / improvement out of this experience, for his ultimate success with social relationships in the world, starting with a most important little girl - their daughter, who has been so inexcusably and poorly treated in this case. I would then make my heartfelt apology (NO justifications, NO excuses - i.e. me, taking TOTAL responsibility for my role as a mom in his life), asking them to share how THEY feel about this - because they may need to express how hurt they are (and not hear you tell them about the hurt you assume to understand them to have, etc.) - that their daughter now has to deal with an experience of this uniquely terrible treatment, language, etc. How awful for a 7 year old little girl (seriously, if it were my daughter, I assure you, I would want the other party to sit there and listen - and to do nothing more than show me, by their ACTION, that they TOTALLY GET what I'm feeling)! Ultimately, I would do NOTHING to justify my son's behavior. I would offer them this - a REAL apology, by focusing on nothing but the impact of my son's behavior on their daughter - totally uncalled for, inappropriate, etc. IF I am lucky, they might accept my apology - and may even allow my son to apologize (expressing a real understanding of the impact it had on her, no excuses) to their daughter and to them, as well. On this note - I don't know about you, but, when we were kids, I remember one of us took a candy bar from the grocery - and was brought back in to apologize to the store manager and offer to make the situation right - it is OKAY FOR KIDS to go through such difficult experiences; in fact, it is important that they do :-). Anyway...
3) Providing the parents understood my genuine sincerity and concern and accepted my apology (and my son's), I would ask them if they might consider, gradually, over a few month's time, assisting in the process of re-socializing him - for his (and their daughter's) benefit. I say their daughter's benefit because, if he does manage to change his choices, it has the potential to be healing for her, as well. However, this may not come to pass - and I would be prepared for this - and prepare my son - the fact is, the family does not need to help him fix anything - they can simply move on and focus purely on their daughter. Either way, he needs to learn a big lesson - and to understand, in the process, that he's not a throw-away because he's made a mistake and, at the same time, he cannot be accepted without making real changes. IF the parents were willing to work with me, I would be incredibly grateful and dedicated. Over the next few months, my plan would be to remind him, whenever he wished to play with her, that, unfortunately, things can't be automatically fixed just because we wish we hadn't done something - things take time and effort to fix. And, if we repeat such behaviors, the consequence is easily that they can never be fixed. Right now, there is a chance to fix things. I would focus on sharing with him that he has the power to fix things - and that I am proud of him for using this time to concentrate on what he can do differently in future. I would ask him what he thinks he could do differently, next time, if she decides to give him another chance. And, hopefully, over time, short, supervised play times could be arranged. My personal hope would be for both children to heal in this process...
I know this sounds harsh - but, in the real world, I believe this is the truth of how things are. People don't have to give him a second chance and, if they do, he needs to know the weight and the potential of such an opportunity. Right now, your son is seven. This is a very impressionable age - meaning, you have an incredible window of opportunity here - a moment to teach your son something very important - a concept that has the potential to impact his life for a highly positive outcome; for a long time to come.
Finally, where this language comes from is another matter I would urg you to discuss / address. If your son is around friends who find this language / behavior acceptable, I would strongly urge you to aggressively work to CHANGE THAT NOW, while you still may have the influence to do so. It won't be long before the judgment of his peers totally eclipses that of his parents, from my understanding.
Anyway - like I say - take it or leave it. I hope I'm not trampling over your heartstrings and being too harsh. I just truly care that you wake up one day knowing you took the opportunity, not feeling you could have or should have. As I see it, taking total responsibility for our selves in life is a HUGE part of the process of growing up. Even at seven years old, a child is learning - either how to or how not to do this in their life. I personally believe that the degree to which we each do this in our own lives (as role models for our children) determines the degree to which we feel happy / successful, ultimately.
I wish you and your son and this little girl and her family a successful and positive outcome. And I hit 'send' with my most heartfelt sympathy for your challenge and respect for your personal strengths as an obviously caring mom!
T. B.
PS - re: the Dennis The Menace mention, my grandfather, Al Wiseman, was the ghost cartoonist and my uncle, Fred Toole, was the writer of the strip (more on ths at http://www.maidenus.com/DesignersNotebook.php) - I assure you, they would not have supported any comparison of their work to this totally inappropriate behavior - I hope people who found it funny at first will, on second thought, consider what could be going on that we don't know about, while a hard-working mom can't be there to police all the time - this is truly, as I see it, a teaching moment for this child.