I don't encourage anyone to be an asshat. I'm an atheist, which means that I don't believe in any afterlife. As such, my (one) life might even matter more to me that a christian's life to him.
I believe we only get one chance to do it right. There is no all-forgiving father figure who will pat you on the back and say: "There, there... It's all right now." When you die -- that's it. No second chances, no forgiveness. If you messed up, you messed up all that you were.

So no, you better not be an asshat, because that would be a waste of the life you had.