[Memory]

It was a good decision for you not to stoop down to their level, so yes, simply ignore those fools. Like you said, you have a better life than them so it should be YOU who should be laughing. XD

I haven't experienced this before though, I'm slim (asian =~=) though I get teased a lot because of my shortness. ;>.> Anyway, I haven't personally experienced this situation towards me although my friends did.
I have been a cosplayer for a very long time now and I do have friends who are overweight and are cosplayers like me. There are times that people laugh at them due to their size but I'd simply tell them to shut up and say stuffs. I just hate those judgemental people.

As for your feeling of escaping, you said it yourself that you think it was because of what happened the other night with those two bastards.
Psychologically speaking, I think you got self-conscious. Not because of what they said but because they said it on that very occasion that you were vulnerable. I never read any part of you crying, just the fact that you wanted to cry, so I think it would be best if you would cry it all out before sleeping. Scream if you must, strangle your pillow if you must. Just let it all out, use up all your strength until you're tired. Then take a deep breath and smile.

This, however, is just me cents ;>.>