Honestly I wouldn't worry about what people say, especially someone on the Internet. Anyone who decides it's okay to say something rude about another person has low self-esteem issues as well and do it to feel better about themselves.
At a con?
Hey, you're probably going to make someone's day cosplaying their favorite character / a character from a series they love. That should give any cosplayer a lot of self-confidence ;>
Currently planned for '13:
Paul Gray Memorial|Slipknot