My best friend of 30 years turned out to be a sociopath and my group can’t see it

I grew up with this guy. He was my best man, I was his. I won’t get into the dirty detail but this year he was caught cheating and split up with his wife. We met up a few times because this was obviously a huge deal and, even though he was clearly the bad actor here, I wanted to give the benefit of the doubt and be a good friend in any way I could. His story was that she was cold to him and that they had a dead bedroom for years and he felt like he had no other choice blah blah blah.

I heard him out, but I had a gut feeling something was off. My wife was disgusted and I admit I got the ick too, but I wanted to reserve judgment and try to be a bro to this guy. Anyway fast forward a few months and he is bragging about all the women he’s dating and basically giving cringe divorced dad vibes and, again, I just got a gut feeling that something was off.

I had meant to contact his ex, who is also my good friend, for a while and we met for coffee. Well… my gut was right. Turns out the betrayal and the abuse had been going on for _years_ and years. His description of the situation was his own little sanitized narrative. Again, I won’t go into the details but my jaw was on the floor. I was completely shocked. His behaviour was beyond disgusting and I realized that I had just been interacting with a mask all these years. I promised I would not say anything as it is clear that he is a legitimately dangerous person and I fear for her safety. The problem is, because I have promised not to reveal the awful truth, I am the only guy in the friend group that knows it.

This guy is a master manipulator and has already been working overtime to make me look like a bad friend and I feel like my group is buying it. I want nothing to do with this guy. I have cut him off entirely. But I can already feel the rest of the group pulling away from me. It fucking sucks. The most disappointing part is even his sanitized narrative should have been bad enough to make people pull away from him, but my guy friends are taking his side. I know I’m doing the right thing for myself by sticking with my values and boundaries or whatever, but I feel hurt.