When David heard what had happened to Tamar, he was very angry. But Amnon was his eldest son and also his favourite, and David would not do anything to make Amnon unhappy.
If one of my followers sins against you, go and point out what was wrong. But do it in private, just between the two of you. If that person listens, you have won back a follower.
Don't be like Cain, who belonged to the devil and murdered his own brother. Why did he murder him? He did it because his brother was good, and he was evil.