I not only used the t word, I added a picture. ?.
I regret that I let myself be dragged into this sorry tale of the domineering and deliberately unkind behaviour that the OP wants us to believe she thinks is right, but apart from that . . .
Having talked to my DD about the thread, I learned that actually, the OP is not the only person who is like that.
In DD’s job, she deals with the aftermath of such MIL problems and with increasing frequency, as DILs in such families pluck up the courage to seek help.
Sadly, she added, some sons are often so used to being dominated by their mother that in their weakness, they are part of the problem.