I agree that this does NOT mean the government can pre-emptively muzzle every theater-goer.
My point was simply, that your right to freedom of speech has practical limits. Never mind the crowded theater example - think about libel, defamation, false advertising, copyright infrigement...
Rights don't exist in a vaccuum - they're always balanced against someone else's rights.
Beyond that, like I said: it gets pretty partisan, pretty fast.
Me, personally? I've lived under ridiculously restrictive gun laws (Canada, NYC). I've also lived under some of the most lax gun laws in the country (Vermont). I think gun-control advocates are completely missing the boat.