What? Simply believing this a crapsack world with no redeeming qualities and that life isn't necessarily as precious as other people believe isn't enough of a reason? Yeah, I do see where you're coming from, but I don't think you have to be cowardly or crazy to simply not want to live. If he believes he'll find greater peace in heaven or simply by not existing at all, then I think that's a great choice for him to make.
Heh, didn't I make a "right to die" thread about six months ago?