Or maybe I'm reading too much into this scene...
Of course, if you think there is no God, it doesn't make a lot of sense to be angry at it...
Anyway, here's the script:
"You see, no one's going to help you Bubby, because there isn't anybody out there to do it. No one. We're all just complicated arrangements of atoms and subatomic particles - we don't live. But our atoms do move about in such a way as to give us identity and consciousness. We don't die; our atoms just rearrange themselves. There is no God. There can be no God; it's ridiculous to think in terms of a superior being. An inferior being, maybe, because we, we who don't even exist, we arrange our lives with more order and harmony than God ever arranged the earth. We measure; we plot; we create wonderful new things. We are the architects of our own existence. What a lunatic concept to bow down before a God who slaughters millions of innocent children, slowly and agonizingly starves them to death, beats them, tortures them, rejects them. What folly to even think that we should not insult such a God, damn him, think him out of existence. It is our duty to think God out of existence. It is our duty to insult him. Fuck you, God! Strike me down if you dare, you tyrant, you non-existent fraud! It is the duty of all human beings to think God out of existence. Then we have a future. Because then - and only then - do we take full responsibility for who we are. And that's what you must do, Bubby: think God out of existence; take responsibility for who you are."