M.W.
I think the trick is keeping it all in perspective. We all feel defensive about the way WE do things and we feel like the way we do them is what might be right for others. It's hard to get feedback that doesn't make us feel positive, and it's sometimes even harder to take that feedback and be productive as a result (instead of hurt or bitter).
I work with 150+ adolescents daily, and they have all been raised with a different parenting style than each other. For the most part, they are GOOD kids and will end up doing well and being functioning members of society. It doesn't matter if they were breast fed or bottle fed, co-sleepers, or alone in their own room, eating all organic, or just conventionally grown food-- if they are getting nurtured and loved and have conscientious parents, they'll be okay. They might experience different trials and tribulations, and will have various outcomes, but most will be okay.
Giving feedback is always tricky. Sometimes friends just want you to support what they are already doing, but afraid to ask for objective feedback. I think you have to really know the person to be completely objective, otherwise it's important to be subjective in the sense that you have to consider their situation (life) seriously. It's not like a job in an office where one could say, "the next time you do this, would you please make sure to....." I think I've learned how to accept feedback by consciously giving compliments first. I always tell my friends what I love about how they do certain things with their kids. Then if/when the time comes to give them feedback, maybe they will feel like I'm being objective and non-judgemental!
Mamas love their babies, we don't want anyone to think we'd do something detrimental to them in any way. It's the hardest job in the world, and we need to appreciate that when communicating.