Is what a father did by touching his son's private parts when he was young considered a sin, and what is the best way to get rid of feelings of hatred and sadness towards him?

There is no explicit evidence defining the awrah (area of nakedness) of a young child, and scholars have differed on this matter. The most probable opinion is that of the Hanbalis, who hold that there is no awrah for a child before the age of seven. From seven to ten, their awrah consists only of the two private parts (front and back). The Malikis are of the view that a child eight years old or younger has no awrah. One should think good of the father if he did not intend ill, and strive to rid oneself of negative feelings towards him, for "the pleasure of the Lord is from the pleasure of the parent." Parents are advised to avoid such actions to prevent negative effects on their children.