I grew up in a home with parents who fought at least every week. Massive scream fests that at time ended up violently. Me and my brother would sleep together those nights. He would wet the bed from all the trauma of listening to these battles.
I was never so happy as when they decided to get a divorce, unfortunately it wasn't early enough for us. Kids aren't alwasy better off with parents that stay together.
The study doesn't claim that kids are "always" better off. But you wonder: What kind of people bring children into the world and then subject them to the kind of behavior you describe? How could people possibly do that--not only to one another but to innocent human beings whom they themselves chose to create? In my mind, the choices are (a) insanity or (b) pure evil.