Your FIL informs DH that you've (meaning me) "ruined Christmas".

How did I manage to do this before Christmas has even arrived?

I called MIL out for the covert smear campaign she started, who knows how long ago, and has actively been engaging in, due to my disengagement from SKID during her visitations. Just the basic "not my kid, not my problem", DH works 6 days a weeks, I have two toddlers to care for while I work from home, and I have ZERO desire to put myself in the line of fire with BM and her high-conflict intrusiveness, disengagement. One in which I didn't announce to anyone prior to doing it, I just did it.

Apparently MIL had been crying for days. Because she was caught and called-out on it.

Yeah, I could have done nothing. Said nothing. But, she had several family members convinced that I "hated them". Maybe it's because I've never been scapegoated, at least to my knowledge, and that it sent me into a brief tailspin, I need to fix this, moment.

I get this feeling this behavior is normal when it comes to disengagement?

DH's family really puts the 'fun' in dysfunction. Bring on the bourbon and Nog.