My dad has recently been caught having an affair with his young personal assistant. Huge scandal; mom was very angry. Now they’re in the middle of divorce proceedings. Mom moved out, the other woman moved in and I chose to stay with him because we’re super close; he’s like my best friend. Now mom’s telling me to go and live with her and go no contact with him cause he’s a bad person and by continuing having a relationship with him I’m condoning his actions and “ignoring her suffering”. My relationship with my dad hasn’t changed, I don’t see why I should end it.
I agree with almost everything you said except 4. is only true for past mistakes. I don't think you should excuse ongoing, genuinely harmful behaviours just because that person will be gone one day. Not that I necessarily think that's what you meant but I wanted to emphasise it.