He can ask his wife to support his right to see things the way he does, and take action as he sees fit. And his wife should never take her parents’ side against her husband. But trying to get one’s wife to see things in the same light as he does is both unnecessary and counterproductive. Although it’s hard, it’s possible to gloss over the way one’s wife feels about her parents, and try to keep her out of the argument, understanding that she feels conflicted between her parents and her husband..
And along those lines, it’s important to ensure that this in-law problem doesn’t become a chinuch problem. The grandchildren should be kept out of the dispute as far as possible. There’s no need, and no justification, for speaking badly of their grandmother to them.
People justify such things, thinking that it’s important for the kids not to be mistaken about the incorrect behavior of the other person. Unfortunately, in divorce situations, parents are often tempted to badmouth the other side, “to make sure they know who they’re dealing with.” This has a devastating impact on the children, and in your situation, it would be very damaging for the grandchildren if you criticize their grandmother in front of them.
It takes a bit of honesty for anyone in such a situation to admit that they are only using their children to further their own agenda, but it is very wrong.
