Preface: I consider myself an agnostic, but I have no beef with believers. I just don't think you can prove the existence of God. It's an act of faith, isn't it? Otherwise, it'd be pretty easy to believe in God wouldn't it?
Rebuttal:
- See: Flaws with Pascal's Wager
- God may know what is right and wrong, but the Church has a pretty shoddy track record (e.g., the Inquisition, the Crusades, the fighting in Northern Ireland, the (past) support of slavery, the fighting in Israel).
- Forgiveness certainly does not require the existence of God. And you really don't have to worry about sin if you don't believe in God (as God is really the one that defines sin, right?).
- Can you explain the Standard Model or the Kreb's Cycle or my dad's weird behavior? I can't, but that doesn't necessarily make me believe in God.
- Yes you can. And evolution does not teach that "Man originated from the monkey".
- I don't know. No one knows. There does not have to be an afterlife just because you might want one.
- Vaguely-worded predictions are bound to come true.
- Yes, by all means, let's return to the morals of our witch-burning, native american-slaughtering forefathers...
- At one point in time, most of the world believed that the world was flat and that the Sun rotated around the Earth. These beliefs did not alter the reality of the situation.
- Maybe.