"Listen, you fuckers, you screwheads. Here is a man who would not take it anymore. A man who stood up against the scum, the cunts, the dogs, the filth, the shit." Those are the thoughts that flicker through the head of Robert De Niro as Travis Bickle in Taxi Driver. And that's pretty much what Seth Rogen is thinking as mall security chief Ronnie Barnhardt in Observe and Report, which is — I should point out — a comedy. Funny as hell, that's how demonic it is. Imagine Scorsese directing Police…