It's the doubling down that's the worst part. The misgendering honestly wouldn't be that big of a deal if they would just apologize and fix their behavior after being corrected. We get it, mistakes happen. Like in the original case that triggered this conversation the user was using a client that doesn't show our pronouns, so they defaulted to "they" instead of the user's listed "she/her". A completely understandable error. But when they get politely corrected and their response is "ugh you Hexbears getting offended is not a good look" or "actshually 'bro' is gender neutral because I say so" then fuck you you're not an ally if you turn into a reactionary the moment you get scratched.
"my most feminine of ladies" is actually a gender neutral address, because you could technically say that to anyone, and language is not prescriptive ok, and and
You don't even have to admit what you did was wrong just say sorry, if this hurts you I'll stop doing it. Even if you think bro is gender neutral to you, you don't need to double down.
Hello opinions are a bit split whether someone minds being called bro or dude if used in the casual slang sense. You can give that as your reason but like just not do it afterwards to them, and maybe stick to only using it with people you know personally in the first place. A trans friend of mine decided a ways back that 'bro' is misgendering and 'bruh' is gender neutral, I'm in punk rock circles where 80s slang is still in circulation and 'dude' is so ubiquitous its list all meaning, but at the same time if someone doesn't like it, we don't call them that, it's just being a decent person.