I don’t have all of the answers, but also had one of these in my life. The weird thing that stopped him was me getting married. It seemed he had more fear/respect/some man shit thing, for a man he didn’t know, than me on any level. I had long suspected that he was a misogynist, bordering on sociopath, but the the almost immediate ‘oh you’re married now, ok’, sort of abrupt end to his picking at me was really quite shocking.
We share a stepchild, ie he was/is a single parent and the child’s mum isn’t in the picture at all, so I had to have him in my life to maintain contact - I love and adore my SC and would put up with anything to have maintained our relationship. I was thrilled when social media took off and we started using that to communicate (me and child), but then he started muscling in on chats, would be casual and sweet and almost like people that could coparent wonderfully, then he would throw in something spiteful or creepy that would go right over the child’s head but it would leave me shuddering and anxious. He seemed to gain real and genuine pleasure from seeing me squirm, and I definitely felt he was delighted when I would try to shield his child from something he was doing or saying, there would be a knowing look, a sort of smug triumph when I would sort of mentally sacrifice myself to keep the peace. Obviously added on to this, I had no legal rights or anything so contact was only ever at his mercy, and he frequently tortured me with it.
Literally the day I got married, he was all sweetness and light, sent his best wishes, and that was that. His child is still the absolute apple of my eye and is thankfully now an adult and living far away from him. We all get together sometimes for an occasion and it couldn’t be more civilised. The thing is, I can see the insecurity in him now, from my new vantage point. He’s just absolutely pathetic, a fucking abusive waste of space who is no good to man nor beast. I have nothing but contempt for him.
To get to that stage for you, I don’t know what to suggest. I do think it kills these pathetic and insecure men to be known. You know him. You know what he is, and he will hate you for it. If he’s ever been vulnerable in your presence, if you know his weaknesses, his shortcomings, then he will be always working to chip away at you, to bring you down to his level so that you don’t feel superior.
I remember how my ex was a serial cheater, but when we broke up for the last time, he was apparently disgusted and appalled that I was dating someone about two months later. I literally went on about three dates with some guy, and was apparently some kind of whore for it.
I paid for most of my SC’s tuition fees, and one term there was a problem with the transaction, can hardly remember what, but he made a big thing about me not really wanting to pay for it deep down because I didn’t think of my SC as my own and didn’t really love them. This is from the cunt piece of shit that contributed precisely zero!
I digress.
I don’t know why any person treats another person this way. But as pp have said, they are convinced of what they consider to be their own truth, nothing will persuade them otherwise.
Oh another weird one. Ex said once to a really very good friend of mine when they were out somewhere with mutual friends, something like “oh, only me and you know the real WarOnPeace don’t we, and what she’s really like, what a nasty person she is”, my friend was gobsmacked and just said something like yes, she was too good for you, you fucking pig. He genuinely believed that a really good friend of mine would be in agreement with him. That really says something about the kind of person you’re dealing with. When their behaviour is absolutely appalling for years and years and years, you hold your head high and continue forwards as respectfully as possible, and they actually believe you’re the baddie of the situation.