You're right, it benefits no one, least of all your DC.
I would stop contact and tell him to take me to court if he's serious. I bet my mortgage he doesn't.
There's another thread running about inconsistent contact. In an ideal world both parents would be fully involved in their lives. There is no reason why separation has to mean one parent is 'lesser' in any way. All that said, I am firmly in the camp of believing that absent parent is infinitely preferable to parent who swans in and out. Inconsistency does a lot of emotional damage because the children never get to process their emotions. It's like picking a scab and never allowing a wound to heal.