The difference between his divorces and Rush's is that Rush is a political and social commentator/entertainer with a somewhat obvious and somewhat loveable emotional neediness, and we can all imagine it might be tricky for him to pick the right woman, and it might be tricky for that woman to put up or keep up with Rush. I don't see him as having 100% great introspection on which woman would be a great partner for him. And he has no kids.
But I think that Dennis appears so informed and introspective of the relationships between the sexes that we do expect him to make the right choices and to put children's needs ahead of his own wants.
I have a teen boy about the age of his; of course that son is going to act tough and SAY that the divorce won't bother him. But now both his parents will probably take up with other people and his life will become very different. His parents will be oversexualizing, right when this boy needs to learn about more than just sex in male-female relationships. I do not think that because a child is a teen that his parents' marriage is meaningless in his psychosexual maturing.
I think the money line of your post is "I think that Dennis appears so informed and introspective of the relationships between the sexes that we do expect him to make the right choices and to put children's needs ahead of his own wants."
It's entirely possible that the right choice is getting a divorce in this case, that's all I am suggesting. I don't know any details, but it's certainly possible.