2 things to keep in mind:
Firstly, and most importantly - you may be 8ft tall and have arms the size of my chest, but guess what - a knife, baseball bat, gun will still hurt/kill you. In this situation it probably wasn't something you had to worry about, but always keep in mind a girl might love you for it but if your dead you ain't gonna know about it!
Secondly - your situation was a fine time to stand up for that guy. It made you look good, I agree with an earlier poster that asking him to come and sit with you may have been better. However, if you just start intimidating people because you CAN or without a damn good reason you will one day come across a guy like me:
I am NOT tall or amazingly strong, but if you start trying to intimidate me I will firstly make you look a complete idiot and if you then decide to get physical (assuming you get the chance) everyone in the area will be on my side and restrain you until the police arrive

Just wanted to share what happed to me the other night. I was at a club with some girls, all of us were dancing and then some random group of guys ran up to them and started grinding the girls ( this so reminded me of what gr9 did in high-school) A thought of "WTF?" crossed my mind and I simply stared at a guy that was to the left of me. In a couple of seconds he noticed me, with the look of revelation on his face he backed off from the girl, came up to me and was like "Sorry man didn't know" tried to give me props, but I simply turned around back to my friends and the kids went off. Now as I remember it, this whole thing just makes me lol. Was this ok or....?

Handled it all wrong, but handled it how a lot of people do.

By shouting and matching them in aggression. I wouldn't recommend it, I have done it my self when I'm not in the mood though. However you seemed to be in control and plotting what to do.

So you should have used the fact you were watching a movie to your advantage, call them out for disturbing your veiwing of a film and not for bullying for some dude.

You would have had the rest of the cinema on your side, instead of just starting a fight like a scene from the film you was watching lol

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