What about adultery? In addition, there are some marriages that become so toxic emotionally that staying together is actually harmful for the children.
You show me one statistic, one study, that shows conclusively that children are better off from a broken home because the two parents could not be adult enough around their children to control their "emotional toxin"...
Folks who are like that, are so selfish they are not going to raise those children any better apart than they do together.
As to habitual adultery, while I wholey condemn it, does not make an argument that divorce is the better path when children are involved.
Again, selfishness is the heart of most divorce, on one or both sides. If you have no kids, do whatever you want... but once you bring a child into this world, that/those children are now the priority of your life. Other than REAL ABUSE or NEGLECT there is no justifiable reason to divorce until the children are out of the house.
Life isn't about getting what you want, sometimes you have to sacrifice for the betterment of those around you. I know such a concept is foreign to the selfish, instant gratification lifestyle that Madison Avenue sells hard.. but its the truth.