I, too, enjoyed that movie a great deal. I have been fortunate not to run into too many moviegoing situations like that in my life, but it does happen. Typically, when it does happen, I tolerate one or two incidents before issuing a menacing "SHUT UP." which usually solves the problem. I think the real problem is one you seem to have hit upon, if not explicitly stated: most people are stupid and/or terminally ignorant. They are devoid of any sort of manners or consideration for others. If indeed the universe is a just one, I will someday rule them all. In the meantime, however, we have to deal with the consequences, like American Idol and poor-driving-related traffic problems.
I'm way ahead of you: http://www.nepentheisland.com/archives/000035.php
I'm not sure I would have closed the van door. How can you be sure it had been there an hour? Did you leave it unlocked? Granted, I wasn't there and I don't know how things actually looked, but at any rate I would have proceeded with caution.