It’s pretty clear he didn’t even know it was a tranny, either. The trans entity had tweeted at him “I bet I’ve slept with more women than you” or something like that, and his reply was just “okay dude.” He clearly wasn’t trying to insult them being trans and wasn’t even aware of it given the context.

On that note, even if he had, ‘deadnaming’ isn’t a crime, it’s a public service announcement. Someone in the room is mentally unwell and needs community support. I don’t personally mind calling someone by another name, and I usually use plurals instead of pronouns anyway, but it would be more productive to challenge their false assumptions on how gender works being applied to themselves in destructive ways. You don’t see some emo girl or guy with an arm full of razor marks and burns and enable that. It’s the same kind of thing.