Why would anyone want to watch it?
Because we're about to see an evil man dieee!
It's not being screened live, and there won't be an audience. However, it will be filmed. This is because the man has reigned terror on millions of innocent Iraqi's and many of them will fail to accept his death unless they get proof (Just like Uday and Qusay Hussein).
I, for one, won't find it morally disturbing to watch this man die. It might be cold-hearted, but it's the gods honest truth.