After meeting people like BoJack and identifying a fair bit with Diane, I would 100% go no contact with BoJack and anyone like him. The others like him in my life whom I can’t get away from, I gray rock or yellow rock (be uninteresting or talk only about the most mundane topics).
Life’s too short to keep someone toxic in it. They’ll only hurt you again and again.
I don’t understand why people think that BoJack deserves other characters’ politeness when he’s rarely polite. It’s mindboggling. She needed to protect herself from him and his strategies to lure her back into his misery. If she’d told him in person, he would’ve had yet another opportunity to do to her what he did to Diane, PC, Todd, Wanda, etc.: lie, manipulate, guilt, overwhelm, gaslight (or whatever other emotionally abusive verb) them into staying for another round of his toxic cycling.
I was ECSTATIC for her that she went no contact.