I say let people think what they want, most of the time they're just jealous because we're skinny and eat pounds of food, while they gain weight just looking at a donut, so they try to criminalize us to make themselves feel better ;)
I've been being accused of being anorexic since I was in middle school and it's incredibly rude and mean in my mind. I remember going to middle school one morning and girls yelling mean comments about me being anorexic at me from across the schoolyard. It sucked. I've always been naturally thin. I'm 5'4" and about 105 pounds. I think I look healthy. And I eat more than any woman I know. And, yes, to whoever said the comment about going up to fat people and telling them to stop overeating...it would be considered totally rude and insensitive to do that, so why do they think it's okay to comment on our weight?
People also always tell me I look really young. The other day an 80-or-so-old woman told me I look like I'm 13 (I'm 23 and I think I look like I'm 23). It really irks me.