Those people who sneer at other cosers for not meeting their "expectations", are those whose lives consist nearly entirely of cosplay. The weightage that cosplay has in their lives is so great that they personally have much to lose, and that is why they are so defensive and snobbish.
The thing is... You can still have expectations of yourself, and be proud of your own craft, without resorting to bullying other people. Not everyone's lives are the same.
You and I, our lives are full of so much more. We have so much more on our plate that makes us smile and thus we don't rely on cosplay for self fulfillment or to stoke our egos.
Only those without healthy, enriched lives, or who have low self esteem (in other areas) will resort to using cosplay to bully other people. It is their only weapon. Pathetic, really.