I think that's the issue: they haven't "become" yet. They're 12, reasonably intelligent (i.e., smarter than a dog), and are looking for attention to validate themselves. They are at that age when they don't know what they don't know, so it's hard for them to avoid coming across as both arrogant and sublimely stupid.

How did trollish people on the Internet become this way? It's like they were born on the World Wide Web.

Haha! Funny thread! Of course then there's that old chestnut, "Well, that's 2hrs of my life I'll never get back."
Tiresome, attention-seeking killjoys that they are

Good one.
EX: "Why was Neo able to fly in the air at the end of that Matrix movie?"
EX2: "Soat the end of the Dark Knight the Joker didn't win?

Ask a question about the film (preferably the ending) that totally doesn't need to be asked by only watching it passably attentive.

Oh, and if the film has two male leads.post a comment questioning their sexual preferences.
Because we all know how GAY Samuel L. Jackson's and Travola's characters were in Pulp Fiction! They were GAY! LOL!