Yeah, and that is getting seriously abused in divorce cases. The courts insist on making a winner and a loser when there is custody of children involved, so there is an incentive to fight dirty. Whoever loses custody becomes a financial slave to the other spouse.
One of the effective techniques is to file domestic assault charges on the other spouse to try to paint them as the "primary aggressor". If successful, that can win you custody of the kids and the accompanying child support award as well.
That being said. The fact is that HE did manhandle her. In most instances, regardless of the desire of the spouse to pursue charges, it is SOP to have the party removed from the home, even if it is to the local Motel 6 or park bench for a cooling off period.
I smell special treatment, that is all.