You have some misunderstandings, I can see. Have you ever hated anyone? You are a murderer. By the way, God does not say, "Do not kill." There were times when he rebuked Israel for not killing their enemies.
David may be your least favourite person in the Bible. He's not my least favourite. He's not God's least favourite either. Jesus was called the Son of David. David was the man "after God's heart".
I'm not advocating a life of sin. As I've said, those who are born again have no desire to sin. They may be weak and fall into sin from time to time. That's not the same thing.