I don't know what to do about my inlaws

[Miltroubles]

My so is adopted.
My Mil and shows a lot of borderline traits.
Thanksgiving blew up!

So and I have two kids and so's brother and wife also have two kids. They live 5hrs away. We see them a few times a year.

This Thanksgiving after dinner they were doing their bedtime routine with their kids when my Mil asked if she could give a bath to my kids as well. After initially saying no I gave in.
After that it was time to say goodbye to the cousins as they were going to bed. Someone asked my 4yr old to hug his 2yr old cousin and he said no thanks. After some pressure he gave a hug to his baby brother. Then the cousins go to bed.
After five min my bil went crazy on my so and said he should be a dad and force my son to hug his daughter. He then said that we were fat and lazy letting my Mil bathe our kids while we sat and did nothing and more screaming expletives. I got so mad (I'm a rape survivor) that I jumped up and yelled back that my son doesn't have to hug anyone he doesn't want to. I just kept repeating that to every rebuke he gave. Apparently hugging his brother made the while thing worse and his kid was heart broken and we should parent. (We have very different parenting style. They would fit the helicopter/ snowplow mold and we would fit the laisser-faire mold)
I said we are leaving and left the room and he followed and kept at it. We finally left with  my Mil crying but no one saying anything.
The next day we dropped by my Mil after my Bil and his family had left and all anyone did was make excuses for my Bil.
Bil sent an apology text to so. No contact since.

Right now I'm so furious with the while thing that I'm ready to cut ties and be done. Bil has screamed at my so like this in front of my children before. This was the second time.
Also no one stepped in and said to stop, that this is unacceptable. Where were their father?

I'm also afraid that my so us basically ignoring the situation and is not dealing with it. Bil knew exactly what to say to cut deep. So is very hurt.

I'm basically getting ready to be the evil one that will keep the family Appart come Christmas time. So... .Yeah. That's where I am right now. I don't know if I should be doing anything. I was so triggered by various things that I needed up having to take an ativan when I got home! That hasn't happened in over a year since I've been in treatment for depression and anxiety that are now very well controlled. I just keep going over and over what happened and I can't believe no one helped. It basically tells me my in laws all think it's OK to force a kid to hug someone when they have said no. So I don't really trust them anymore.

[my_memories]

Welcome to BPD family! I noticed you said that they rationalized your BIL - did anyone empathize or feel bad for your SO? Drama is such a big part of having a member of the family with BPD, they tend to surround themselves with enablers.

Edit: I just realized that this all came down on Thansgiving! I'm not sure if there is research on this but I have a personal theory about BPD and the holidays - maybe it's the opportunity to have all eyes on them, I don't know, but something about the holidays has always been a trigger point. Anecdotally, I've found most people I know with a BPD connection have a love/hate thing with holidays. The BPD parent either goes above and beyond (a real high, where the family seems normal
and lacks its usual chaos) or the holiday is an opportunity to have the abandonment issue triggered. Has there been issues on holidays in the past? Does the family of your SO know of your history? If so, it makes the whole forced affection thing seem like an overt action to engage in conflict. Anyway, sorry for my random thoughts.

[Miltroubles]

No one has indicated that they feel bad for us. They just made excuses for which my Bil acted the way he did and the other thing my fil mentioned is that my Mil is very sad because she values joint family time above all else. (Actual quote). In the past holidays have been small drama only. Usually my so and his brother can work things out between them when Mil has increased the drama artificially so she can be seen to save the situation. In fact, the sat and sun day went really well because we were all in a group chat for the continuously changing plans and there was no way for my Mil to meddle.