Predestination destroys you! If every action is caused by God, then I do nothing. If I think; therefore, I am. If God thinks; therefore, I am not. It is like God is playing ventriloquist in my brain. Where is the moral agent, where is the thinker, and where is the I? Am I some puppet to teach another person a lesson with?
Predestination makes God a sadist! When God punishes people with Hell for not being a particular faith, God is damning them for what it did to them. This is what sadists do! Have you seen Hell, it is not pretty?
Predestination makes God the only sinner! If God is the one committing every action, God is responsible for killing people, for terrible diseases and for the Holocaust. Don't even tell me God never promised that bad things would not happen (C. S. Lewis) or it is the gays' fault (Pat Robertson). Well, God can just write off himself by redefining what good and bad are. Some Christians believe that God changed the law after Jesus died, but that does not mean the old laws are not reprehensible and God's fault.