I just went to the pub for food, found an empty table and sat down.
5 minutes later this guy comes over saying "I was planning on sitting there!!" - Trying to work out whether he was joking and what he expected me to say I just about managed to get a sorry out before he lay into me and started swearing.
Going on about how "youngsters are always on their fucking phone" (I was finding out where my friend was, not that it matters) and started moaning about me to everyone around him, saying that he won't dare say anything to me because I'd probably bash him. 
For one, I wouldn't bash anyone. And he can't have been that scared to say anything..
And then he kept getting up from his table, which was identical to the one I was at, and slowly walked past, dramatically glaring at me. Bizarre.
AIBU in thinking that unless you'd already sat down and claimed a table, then you have no right to complain that someone else was sitting there already? There was literally 5 minutes between me sitting and him coming over, I didn't run past him and barge him out of the way. IT WAS A FREE TABLE.
Had he jokingly said oh damn I was just on my way to sit here, I would probably have got up and moved like the pushover I am. Except he launched straight into a tirade so I told him to get a grip and ordered a fuckton of food to forget about him.
Arsehole.