I think the best thing to do is to avoid talking about Mom when you are with Dad...and don't talk about Dad when you are with Mom. I know it is hard, but it is no fun being in the middle. Just let them know you love them and are there for them. My husband(whose parents have been divorced for about 40 years) still feels uncomfortable when Mom talks about Dad to him...and when Dad talks about Mom to him. You are stuck, because if you agree with them the whole thing of liking one other than the other comes into play. How childish is that?