My ex is uNP. I think you are spot on with him painting you black because you've moved on and don't supply him with what he needs. I could be totally wrong but here is my take... .
If you don't indulge his advances and give him supply, it makes him feel abandoned, rejected and possibly other negative emotions. I think deep in their mind they know that we were good but to treat us this way would make them have to face that if we are good that maybe it was them that were bad. In order to not have to examine themselves, they blame us and treat us poorly because it reinforces their mindset about us being bad.
His ex is creating a supply for him, why would he jeopordize that if he is getting what he needs? No need to paint her black, if he did he wouldn't have someone stroking his ego giving him what he needs.
That's very spot on. I've posted about this before but he kidnapped our child out of daycare a few weeks ago. In my frantic state of mind, I gave the police every single person I could think of that he would have fled to, his ex wife was one of those people. She actually defended him to the police. She told them that I never allow him to see our son (which is a very big lie, I give him extra time outside of our plan constantly) and that I was a crazy person. She and I have never even interacted face-to-face. So she is definitely validating his thoughts about me.