If you are divorced, never say anything bad about your children’s other parent. In fact, don’t even refer to him or her as “Your father” or “Your mother.” You are the ones that chose to have children with each other.
Mom referred to my dad as “S**t-head” most of my childhood. How can that possibly help any child whose parents are divorced? In the end, of course, I was angry at Mom for calling him that, for her lack of ability to be the grown-up in the situation. Kids don’t actually care what happened; they just need to be cared for by both of you.