I’m sorry you’ve had to experience that transphobia on Lemmy. It is unfortunately common. And sometimes it even lurks as internalized transphobia in people that do not think of themselves as transphobjc. For example, there are Lemmy instances that actually promote chasers.
I believe all instances if transphobia should be called out and obvious examples should result in bans. Sometimes it is good to let people have a chance to accept criticism and retract but I am biased towards more often banning. Comments that are transphobic should also be removed.
Oh yes, sorry if I implied giving these particular people a break. I was speaking more generally but miscommunicated. The people you mentioned should all be banned in my opinion.