That's my understanding of Calvinism as well. And I simply can't read that any other way than to believe that it means God decides what sins people will commit and then causes them to commit.
Your understanding of Calvinism is correct then at it's initial point. Your second statement shows the problem in your understanding. It would be correct if you said "it means God decides what sins He will allow people to commit and follows through on permitting them to do so." God doesn't have to author sin in man at all...man quite ably does so himself. God's omniscience allows Him to both restrain specific acts of evil and actively allow others, both according to His purpose.
Again, if you would return to the discussion at hand regarding man's will and how choices are made, I could better explain why Calvinists can believe in the above statement without man being an automaton and God being a sinner. It seems to me that it's only your obstinate refusal to discuss this rationally that's keeping you from at least having a proper understanding of Calvinism. Whether or not you agree with it is another matter, but at least you'll have a correct understanding of it. You seem to have no interest in even trying to understand Calvinism at this point, which makes your outright denunciation of it rather rediculous. I can't speak to the effectiveness or patience in other Calvinists who've attempted to 'answer your questions' but I can offer my willingness to do so as long as your actually interested in understanding the position and not just determined to refute anything I say simply because it's "Calvinism."