Yeah, this guy hadn't set out to be obnoxious, the way school kid bullies do. Bullies are doing it purely to be cruel, because they can and they want you to be miserable. This guy wanted me to listen to him and was annoyed that I wouldn't, but he was more in the "I will force you to want to listen to me and somehow this will work" mode than "I will punish you for not doing what I want".

And I never felt in any physical danger, not even when he was trying to box me in. Much safer than a kid on a schoolyard. Of course, that's because I was in a coffee shop with plenty of people around. If I'd been outside alone I definitely would've fled from this dude. :/ But while that would've felt more dangerous, I don't think this guy was a serious threat. Just that not-all-there kind of unsocialized behavior.