Why would someone who is “really” a woman “want to be” a man? Easy: She’s experiencing sexism, and she wants out. So do you, but you are fighting sexism the right way, by being a feminist. This other person, who claims to have “gender dysphoria,” is just trying to cut to the head of the line. They’re cheating. They’re trying to become the oppressor rather than fighting the oppression. Why would anyone be a trans man? Because they’re a bad, sexist person. That’s the only possible answer. After all: It's not like they will literally die if they don't transition. Right?

If they want to be men, why, you’ll treat them like men! But with a particular, angry emphasis, because you view their manhood as a betrayal! And this is not only feminist, it is trans-inclusive, because you’re treating them the same way you would any other guy!

They aren’t “any other guy.” They’re trans guys, and you’re a cis person, and as such, you hold social and political power over them, which you are ignoring in order to assume total authority over an experience you do not share, and (this seems pertinent) to get away with treating somebody like crap because they are transgender. You're not treating them the way you treat "any other guy," you're treating them the way you treat trans guys, and the way you treat trans guys is: Bad.