As someone who has been on the receiving end of this kind of action (uN/BPDstbx stopping all contact unilaterally, going to court to get an ex parte motion to deny parenting), I urge you to think carefully about it before you do it.
In our case, my SO did yell at SS. He contacted his mother who swooped in and "rescued" him from our home. She refused any contact with us for a month. She took him down to file an order of protection against his own father and used the therapist to try to get all parenting time stopped. It was contagious and SS was unable to stand up to her. To some degree, I think he WAS upset with his father and a little anxious about coming back over and dealing with the fall-out of the incident that happened. But that doesn't mean he wanted it all stopped.
If you stop him from seeing his dad, he is only going to get more frightened and it will only be harder to go back. I understand that what your ex did scared him, but this is an extreme reaction, IMO, much like SO's stbxw did.
JMHO. There may be middle ground.
Good point. In my case, N/BPDx was having some kind of manic episode that he is having a hard time explaining away. My L was behind me 100% in stopping all overnights and the emergency motion was the responsible thing to do. So there is definitely a middle ground, a low, and a high in these kinds of situations.
But it's good to know that it is a tool you can use if you need it. Not easy to gauge the best time to use it, but it's there.