There's a bunch of believers, in many subjects, who use anger to press their points. This is a good example. I recommend not having the volume too high:
Quite hard to know how (or if) one should address such a person. She makes several statements that are obviously wrong, and could quite easily be explained if she'd listen. But it seems pretty likely she'd just shout more.
Probably the best approach would be to just say as little as possible, like:
The Truther in this video is Jeremy from WACLA who also appears in WITWATS confronting congressmen at the end of the film. He's famous for interrupting speakers with 911 rants including a live broadcast of Bill Maher's show.
I think the key thing is to know when you are wasting your time. Some people can be reached, and in reaching them you might have a magnifying effect and other people might be reached. But if someone seems so totally beyond all reason then it's not really productive to engage them. I can see how in a live forum like Hitchen's, where they are raising off-topic nonsense, then the best option is to just let them say their piece and not respond. Here, where time and space are not in such short supply, I think it's worth a shot at least in planting some simple seed that might bear fruit eventually. Something that might make them, or at least some reader, rethink.