>it's a choice, after all.

What about religion. It is an interesting intersection of 'is a choice' and 'protected demographic'. And why should it be any more acceptable to harass someone for what they choose? Is it more acceptable to discriminate against a Hispanic individual for choosing to identify with their heritage (a choice) than to discriminate against them for being Hispanic (not a choice)? Both seem wrong to me.

>that's not something I chose. I was born that way.

What about those who are of a different gender/sex than they were born? What about people who choose to change their gender?

Even your response itself can be an issue, as there is an implication that others are born a given gender and cannot change it.