This mother who spoke to you had an iota of truth in a mess of ignorance, in my opinion. And what she should have been speaking about was the possiblility of social 'otherness', not school shooting. Sheesh....
I could write a very particular post on this, but won't. I'm in the same boat as you are. I am a mom who some people would say "shelters" my child. I'm pretty unapologetic about it, though. We are household which strives to model non-violent behavior, and letting my son be exposed to that sort of media is in conflict with our family culture.
The woman who spoke to you was doing a great job at showing off her amazing social skills and education, wasn't she? ONE- there is no pychological evidence that not allowing your child to watch mainstream tv and listen to the radio will make a person violent. I can't even do the mental gymnastics to work that one out, really. TWO- what exactly was *she* modeling for her child? How to be rude and intolerant of others who are parenting differently than she is? Umm... just my opinion, but that sense of entitlement to belittle others *can* be passed on to kids, and that particular sense of rudeness is something that will more likely be a detriment to her child, socially. The other mom was trying to bully you to legitimize her own behavior to herself, because if she knew it was "okay", she would have let it go.
Certainly, a lack of wide exposure to media in this culture can sometimes make a child appear socially 'other', and that is something to think about. You can broaden your child's exposure to good kids music just by going to your local library and checking out the kid cds. (I personally go nuts with just kid music, so we do a lot of jazz and non-offensive pop and rock. It's out there....just not on the radio so much.) My son didn't watch any 'kids tv' until last summer, when we decided that he was ready for some of the themes and storylines of "Dinosaur Train" (he was four at this point). Up until then, he watched concert videos and Mr. Rogers, because that's what he liked and wanted. We don't watch tv around him...we wait until he's gone to bed, or unless it's a video that's appropriate for his age, and even then, sometimes he's the one to say "I don't like it"....
I respect his need to have a *childhood*, I guess. For me, that isn't about imposing my world on him, but by being respectful and understanding that some media introduces situations which he doesn't have the tools to understand yet. Nor should he.
And if you haven't checked it out, today's featured mamapedia post was on Facebook and adults friending their children's friends, as well as bringing up the controversial 'lying about their age' to get kids younger than 13 on facebook. The author was mostly jeered by the comments thus far, with few exceptions. Some people feel justified in showing their kids that lying is okay when it works for you, and so is breaking the rules, so long as your kid is participating in the common culture and not feeling left out. Where are the lines between an 'adult' thing and a 'kid' thing? We don't give them alcohol, we don't let them drive, but the line between 'adult' and 'child' is becoming increasingly blurred. The lack of distinction between how children and adults dress or spend their time is disconcerting to me as both a mom and a preschool teacher.
MM, there are others like you! You are not alone.:) If you want more resources, check out blogs like "Empowered by Play" or TRUCE (Teachers Resisting Unhealthy Children's Entertainment). These have great sugggestions for fun, healthy, stimulating activities for kids and their parents. Don't let this other mom get you down. You are the parent to your son, you have to make reasonable decisions for your child. Not necking in front of your son, not turning on the popular radio station or letting him watch 'whatever' on television isn't going to turn him into a homicidal maniac. There are plenty of things that contribute to creating a murderer (parents with unchecked, severe mental illnesses, parents who teach their child they are entitled to anything, parents who bully and teach bullying, bad brain chemistry.... ) but not letting your kid listen to Kanye West or some other Radio King when he's three probably isn't one of them.