There are a lot of bad things in the world - the holocaust, genocides in Darfur and elsewhere, executions, suppression of women's rights, the crusades, just about every war, terrorism, etc. Pascal said, "Men never commit evil so fully and joyfully as when they do it for religious convictions". I don't know if that's true or not - you can be plenty evil without a religious background (Stalin/Pot/Khan/etc).
Does satan exist and if so, does that make Hitler less culpible for his acts because he was under the influence of satan's minions? Is the common street mugger also acting on satan's orders? I think to raise this explanation vitiates man's sense of justice and morality. Can we put the mugger on trial if he is sane but claims demons made him do it?
This is a great question! Why have we? Is it evil if I take a knife and carve up a live cow while it dies in agony? I would say yes, absolutely that would be terribly evil and something I could never do - it would give me nightmares just to think about. But is it evil when a pack of coyotes do the same thing with their teeth? How about when we raise millions of cows on farms and send them to slaughter? How do we know something is evil?Why has man evolved to be so good at evil things.
Let's say we went to some remote island in the south pacific where they've never heard of jesus or the ten commandments, etc. And we killed one of their tribe. Do you think they'd think we were evil? I'd sure think so! And where does this sense of morality come from? I'm an atheist and you're a theist and we could both agree eagerly that rape, murder, theft, lying, etc are all immoral. I don't need god to tell me and you don't either just as Hitler didn't need satan to commit atrocious acts, he was evil enough all by himself.
And all of this raises even more questions: if we're going to attribute evil in the world to satan, why doesn't god intervene on our behalf? Why doesn't he stop satan today and prevent evil in the world? How can you worship an omnipotent god who allows the needless suffering of pious people?
You don't believe in hobgoblins but you do believe in the "evil one's demons". Where is the evil one presently? What if I wanted to worship satan and do his bidding, would he then appear to me since I'm on his side now?
All of these "good things come from god" and "bad things from satan" is a cop out in my opinion. If a person donates their time to charity, I say kudos to her! I don't think god made her do it - she does it because she's a good person and mindful of her community. Similarly when I read in the paper of someone killing someone else. I say, shame on her! I don't think satan made her do it. We are all responsible for our own actions - to say otherwise eliminates responsibility for misdeeds.