I'm no family therapist. I know far less about family counseling than highly trained, full-fledged family therapists do.
But one thing I do know is that parents should never fight in front of their young children.
A husband and wife fighting in front of their kids can be frightening for young ones. Hence, it's unfair to children to have to see their parents fight each other in a heated verbal battle.
If parents feel the need to fight each other at home, they need to do so when their children are not home.
Sure, if kids parents are very angry at each other, their children will sense it, even if the parents don't fight in front of the kids. Children aren't stupid.
However, it's still a lot better if the parents refuse to fight each other in front of their kids. Parents fighting each other in front of kids is unfair and unacceptable.