Soldato
I'm over half a foot shorter and a couple of stones lighter but I would have stood up for OP and escorted him out of the cinema.You did what everyone else should have done. If it happens again, repeat the same action. If I saw 6 obnoxious guys picking on 1 person, I'd step in. Being 6ft5 and around 16 stone helps though.
Like I said, ask the nearest stocky man for help. I'd be shocked if you were refused.