I have a few thoughts, OP, as someone who has been in a situation with truly toxic in-laws. First, I’d probably explore why it bothers you so much that they are who they are, and that they have been allegedly awful to you. I understand it isn’t nice. My in-laws (including BIL) have hated me from about the moment they met me. They have called me names (like slut and whore) and have told both DH and I that I destroyed him and their family. Before we married, they left messages on DH’s phone begging him to not go through with it. I actually find it quite sad, as I would have loved to marry into a normal and close family. I’m from such a small family myself that I would have really valued a close relationship with my in-laws. As for how I feel about what they have said, it’s just water off a ducks back. I know I’m not a whore or slut, and I know they are nuts, so why on earth would I feed into the drama.
I obviously can’t have a relationship with my in-laws and have needed to limit my communication with them, but I’ve never influenced DH and his relationship with them. I understand families are complex, and his parents have their own trauma. He has always stood up for me but I’ve never made it a battleground. He has actually cut them off in recent years due to his own conflict with them. I’ve told him honestly that I wouldn’t have made the same choice in his shoes, but I respect his decision.
The fact your husband didn’t tell you, suggests he probably does think of you as controlling, and he was worried about your reaction. If my husband told me he had spoken to his parents, I’d just ask how he felt about the conversation and how his parents are travelling. He wouldn’t need to worry about letting me know.
Don’t get me wrong, I haven’t been a doormat. Due to the volatile nature of my PIL, I’ve needed to put in strict boundaries around their contact with our children when they visit (never unsupervised). It’s absolutely a situation that I wish were different, but I think if you step out of the drama and the wounds to ego etc from them being awful, it will be a more peaceful space to be… and you can just be a partner to your DH as he navigates his own relationship with them. Being overly controlling and him feeling afraid to tell you stuff, probably just adds to the confusion and MIL’a voice in his ear saying you are the unhinged one!