I eventually ended up saying to my oldest son, only last year (and he is nearly 27) that people have every right to leave a relationship that they aren't happy in. That they really need no other reason than that.
That way, no blame was given to his very narcissistic father; as anything that incriminates dad, is just asking for trouble.
I think that approach was very freeing and empowering for both of us.
My kid's Dad had told them all kinds of lies and nasty blame games as to why I left. He Is not one to take responsibility for anything or be honest.
I copped a lot of shunning, judgement and being labeled "crazy" in a stigmatizing, demoralizing, invalidating way.
It sounds like you are going through something similar and it's a really horrid, painful, subtle, manipulative form of abuse.
I'm so sorry and sad for you that you are going through this.
I had to stop seeing my kids when they were being used by him as minions in his abuse campaign and it's extremely painful, but I had to put in boundaries that basically communicated that I have a zero tolerance for being treated abusive, any more.
This, unfortunately, went on for quite a few years. But we are coming out of it now.
I reduced contact to birthday and christmas presents and cards, with heartfelt and honest letters, but avoided too much story about myself and their Dad.
The more you know yourself, accept yourself, love yourself and practice self-care, and surround yourself with loving, accepting respectful people, the more strength and positive role modelling you will give your son.
My children and I no longer speak of their father. If he's mentioned, it's in very light, routine terms.
However, when his behaviour has been off the charts criminal, either abusive or over the top negligent, i have had to call the behaviour and I've been clear that it's the behaviour I'm objecting to, rather than an attack on his person.
This was only done with my younger children who couldn't be poisoned against me though.
The older ones were tricker to talk to about those kinds of abusive, manipulative tactics that they were subject to.
I just had to stop talking to the older teens and young adult chidren while they bought his side and waged a blame/smear campaign against me.
I had just been too ill by the abuse and my c-PTSD and acute stress disorder plus a host of long-term physical issues. I was run down and shattered by long term neglect and exhaustion.
He wanted the kids, wanted to have a "win" " against me, knowing they were my everything.
I was the one to leave, I had poverty, homelessness, illness etc so the older kids were easy to sway and keep from me.
When it is too painful and unfair and not honest, it is very hard to get past the hurt of blame, rejection, denial and betrayal and maintain a loving, accepting mode while practicing healthy boundaries. But striving for that and modelling that, gives children security and counters the nasty slander and denial of responsibility coming from the other parent, I've found.
I hope you surround yourself with love and kindness and that you are getting (or can get) lots of support around this.
I also hope you can accept that your son may stray from being your loving boy but part of growing up often involves a separation from mum and a closer alignment with Dad, no matter how Dad behaves.
Hopefully, as he matures, he will see things more clearly for himself and you can build a healthier, closer, respectful and healthy-boundaried relationship.
I hope some of my story gives you some helpful ideas and support to get through this.
This kind of thing has been one of the most painful things I've had to go through, so I am sending you lots of compassion, empathy hugs and e-support.
Please feel free to vent and I am happy to listen and give you peer support, if you find it helps. Good luck!