All I can say is: Rock. On. I totally would have done the same thing. The telling-them-to-shut-up part, not the kicking part, because I am Feeble, yo. But I'm very easily annoyed at the movie theatre myself (it could be why I rarely go and see any new films these days) so i totally get you.

There are only two things in the world that piss me off to the point of speaking up, and that's people talking through a film, and people who cut in line.

Go you for smacking a bitch!

(On a side note, was the movie completely ruined or did you still enjoy it, even just a bit?)