Some must be punished. We, each of us, do this privately, choosing lovers and friends on their evident merit, shunning others because they are evil assholes. But justice excuses no one. If dad is an asshole, he should be disowned. It is specifically evil to exempt someone from justice because he is a blood relative.
Justice is thicker than race, religion, or kinship.
The notion of divorce exists, because your liberty cannot justly be held hostage by a spouse. Although it was 25 years ago, I remember them still, a little knot of tipsy, gregarious law students in a State Street bar. They were partying, soon to graduate from UW-Madison's reputable school of law. They hemmed and hawed. A boy giggled 'injustice'.