Aye, it is kinda rough when you're just randomly judged by your character. However, when this happens, why not just calmly explain why it's no big deal that your character is different from your real gender?
This way, maybe you'd be able to make peace, and let them see 'why' people make different gender characters.
After all, the characters we play, are played because we like them. Simple as that. *Shrug* It's not an avatar that is exactly what we look like, the same way their character doesn't look exactly like them. We don't have (actual) humans running around here, anyway, and all humanoid characters are used on an animal model. So in that case, every character is really quite different from whoever made them.
It's just a favorite character, and if you like them, that's what matters. <3
But, if they still heckle you? Myeh. Let them run along, then. xD Chances are, if they don't like your character, they'll run off eventually to go do what pleases them.