This is something that I've tried to get Bel to understand more than a few times. My guess is that he does understand it but simply chooses to ignore it. Admitting that atheism is simply a lack of belief would destroy a lot of his other arguments. But what he doesn't understand is that he's not even really arguing against atheism. I think we would probably take issue with a lot of these so-called atheists that Bel also takes issue with.
If you're frightened of dying, and you're holding on, you'll see devils tearing your life away. But if you've made your peace, then the devils are really angels, freeing you from the Earth.