BlueRose
If he is a good friend of yours, take him aside and point out to him that what is wife is doing is abusive. He may disagree with you at first because, no doubt, his self-esteem has been battered. I'm also willing to bet that he grew up in an abusive home and considers what his wife is doing to be "normal".
Point out to him that it isn't normal---it's degrading and humiliating. I don't know if they have any children but, if they do, also point out to him that this is a toxic environment for the children. Urge your friend to do one of the following --- 1) Get counseling. If his wife won't go with him, then he should go by himself; 2) File for divorce. If he goes with this option, he should document every incident of abuse---not only to him but to the children.
If there are any children involved, he should arrange for them to get counseling, too.
I grew up with an abusive mother. To this day, I wish my father had grown a backbone and done something about the toxic environment.