(1) Many of the griefs we see (robberies, murders etc.) ARE a result of other humans’ sin.
(2) I’m not saying that Satan-less human sin isn’t theoretically possible, only that it’s apparently how God arranged things with respect to our local fallen creation. Adam and Eve had nothing to be ashamed of until taking what (uh huh) the serpent offered. Why this and not some lone human disobedience to God was the prototype of all sin, I think there has to be a reason.
When you are tempted, you shouldn't say, "God is tempting me." God can't be tempted by evil. And he doesn't tempt anyone. But your own evil longings tempt you. They lead you on and drag you away. When they are allowed to grow, they give birth to sin. When sin has grown up, it gives birth to death.The popular idea that sin happens as a result of Satan or one of his demons coming and whispering in one's ear is the same sort of myth as that which posits God as the ruler of heaven and Satan as the ruler of hell; the angels and demons fighting over one's soul, one whispering in one ear, the other whispering a contrary message in the other, trying the pull the person one way or the other (the funniest example seen in South Park Episode, Ike's WeeWee, when Mr. Mackie gets tempted to drink after getting fired for losing control of a lid of Columbian red). It's popular imagery that's more Zoroastrian in origin than Christian.