The proper response to transphobes is 1) “you shouldn’t say x”, and if they don’t, 2) “shut up, idiot”. There’s some subset who would be respectful but don’t know that certain things are disrespectful, that’s what #1 is for. The rest are just idiots trying to fit in with their fascist group dynamic. They’ll happily out themselves when you ask them to speak respectfully, so for them, it’s #2.
If they try to have an argument, just respond to everything with “who cares? leave them alone.”