The great thing is that you are absolutely correct - and you can see it in how they respond. Apologies and corrections are most commonly used things when people realize they have misgendered and/or deadnamed someone. And when it is someone whose gender has been clear for a dozen years (and pretty much known for several before that), then the offending person should definitely feel extra shame in misgendering - and if they don't feel bad or make any correcting effort, that tells me that in fact that they don't care about misgendering.
Here is the thing - you had opportunities to correct your casual bigotry, to show that you are not a transphobe ... but you have specifically chosen to not only double down on your bigotry, but to also pretend that the person pointing out your hate is the problem.
Nope, sorry - you're the bigot. You're the problem.
As for me being a moderator, more than that I am a human - and because this forum is dominated by cis-het white men, there is plenty of casual misogyny, racism, homophobia, and transphobia. As a human, I try to help people be better when I see that stuff. Sometimes it works, sometimes the person doubles down and shows that it was actually intentional - that they don't see their bigotry as a problem, because that is who they are. You had your chance, you chose to be a bigot.