I've gotten flak for saying "look man" once. Getting bent out of shape over misgendering in these kind of contexts is silly. I don't think he means anything by his use of "boy", other then being rude but it has nothing to do with your gender. I also used to get misgendered in real life and it never felt like something I should get mad about when it's a simple accident.
Obviously, this doesn't apply to what the trans and nonbinary community have to deal with, where they are purposefully and maliciously misgendered. I just don't think that is what's happening here.
referring to trans people as they (an outer group) and the general cis audacity the comment exudes. even if they're trans, they should stop acting like an insufferable cis