well, if you're talking about Mtf being sensitive about the subject, it's because there's generally much more stigma attached to males who are transgender and gay males than gay/bi/trans females. Alot of that comes from other males, though. I don't see girls harassing guys for that. But there's still this aged, lingering idea (in the west at least) that guys should be as masculine as possible, and if you aren't, you're a freak etc.