I don't know him very well, either. But while I haven't been getting any "rude" replies from him, I can say that I've seen some, let's say, very questionable posts from him. Some of them seemed to have a hostile tone in them. It was as if he was trying to exert his intelligent and superiority over someone else to stroke his ego.
I've seen the same attitude from high schoolers and other not-so-nice places on the internet, so it bugged me when I saw that from him. Not that I want to throw shades at anyone, to be clear. And the other guy could have handled the situation better as well.
"It's not what you say, but how you say it."
I don't know if the rudeness was done on purpose or if there were some communication issues. I believe a sign of a mature person is being able to express yourself and convey your opinions without figuratively taking the piss out on everyone else. That goes for
both of you all of us. Worst case scenario, just block each other and move on. I'm not good at communicating, either, and someone told me I was often being passive-aggressive. We talked and sorted out our misunderstanding. So don't anyone take what I said personally.
If Theo still wanna argue, 1v1 Yanfly somewhere else and let everyone see.