I don't think he crossed the line. Yes, he was making light of a tragic event but he's actually making fun of the movie not the people that were killed. He's also making fun of people like us who say things like "I'd rather kill myself than watch..." It's silly sometimes how serious we take things as trivial as movies. Don't get me wrong, I'm not a Cook fan nor am I defending his "comedy." I'm just saying that he was far from crossing the line.
On a side note, I do have to say that I was a little dissapointed by the lack of "darkness" in The Dark Knight Rises. This is basically the climax of the film: