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.
OP you have given us way little information. How was your parents marriage before this blow up? Were you not close with your mother before? You mention you are close with your father but nothing about mother. Also were you upset or angry by the actions of your father? From the information you have shared (that you are staying with your dad and his mistress), it seems that you are not bothered by what is happening.
Now based on the limited information you have given, your father is clearly the guilty party here. He did something that is morally wrong. Hopefully you understand that. Your mom is very hurt and must feeling betrayed (slightly even by you because you chose to stay with your dad and his mistress). In that emotional state, she is making a unreasonable request to you (to go no contact with your dad). If you want a good relationship with mom, you will have sit down with her and reach an understanding and compromise with her. Maybe you can go to therapy with her like some other commenters suggested. One thing I am sure about is that if you side with father on everything, you will end up estranged from your mom.