People don't upvote it because it's funny or original, they upvote it because it confirms their worldview. Many men feel really threatened by the idea of transgender people being tolerated and generally allowed to exist because they see it as a threat to their own sexuality.

Of course it's a faux pas to go around openly admitting that you have a hatred for a group of people because they are different than you, so you have to do it subtly, making jokes or, more often repeating jokes because 'hey, it's just a joke, get a sense of humor', right?

See also people who begin sentences with 'I'm not racist but . . .' and then proceed to make some sort of racist joke or remark.