Maybe she will be resentful later on, as well. It goes both ways.
If it's as bad as you say, and this is ruining your holidays, I don't see why you have to even go. You don't have to keep him from his family....let him go, but you are not 'obligated' to go every time. You have a right to enjoy your holidays,too. And you should definately not be obligated to be around them "every weekend"--that's a bit extreme; you do have a life, too. And I think your husband should respect you as well, and not force you to be in a miserable situation so often. He needs to compromise with you, too. I spent many times being subjected to certain in-laws that were horrible to be around (rude behavior, way too much/constant at times drinking, back-stabbing each other, excluding certain people from conversations and situations, putting up with verbal and emotional abuse from the mother, etc....) , and after many years, I decided that my needs and happiness were important, too, and I decided not to subject myself to that misery anymore---except on rare occasions. And you know what? I am so much happier now.
If it's not too bad, go sometimes, but don't let anyone tell you that you are "obligated" to participate every time. By the way, where does your family fit into this picture? Oh, and I agree---these people will not change, so best to nip this in the bud now.