We just had a conversation about sharing/being kind vs being a pushover last week with our kids. I think it's all part of the same conversation: peer pressure, bullying, excusing behavior. I DO believe that kids will be kids, but there needs to be limits to what that means.
http://viewsfromthecouch.com/2012/02/12/you-didnt-thank-me-for-punching-you-in-the-fac/