My ex had a divorced mother who sometimes needed help, and he always did try to help her. However, he didn't tolerate disrespect.

The one and only time she called and insulted me, he hung up on her. She called back, he hung up again. She never said anything negative about me again to him. Don't get me wrong, if I'd been mean to his mother, he would have confronted me about that. It wasn't taking sides so much as insisting that everyone be respectful.