[Allyson]

I try to look at it as why should I let some stranger affect who I know that I am?  If they choose to be that petty, mean, immature and selfish, what they think of me is totally irrelevant to me, and they really don't want to know what I think of them.  They have not earned the right to criticize me, or anybody else.  

I don't mean this in an angry or nasty way, but why should I give someone like that any credibility to affect my thoughts negatively?  
In short, I don't really care what they think, and just let it roll off like water on a duck's back.  The problem is in them, not you.