Well, for whatever it's worth, I'm not really attacking you, or anyone else for that matter. I think OP is overreacting a little, but I certainly understand why they find the joke upsetting. I think it's a bad joke. I look at it and just go, oh Jesus, not funny dude. I don't know if I would call it a transphobic joke, but, as a cisgendered individual, it's not really my place to decide what is/is not transphobic. In my mind, it's the kinda joke you immediately make off the cuff without thinking about it, and then immediately regret. We've all made those, myself included, and sometimes we pay consequences for the things we say, even in jest, myself included. The best thing to do is to make a sincere apology, commit to trying not to repeat the mistake and move on.