The bias against women? Women are granted primary custody in overwhelming majorities of situations. It might be difficult to normalize the samples to eliminate this bias I guess. The current domestic violence model is heavily biased against men but you don't see it being challenged.

Lets be open minded that Alienation and Abuse can be caused by either gender. While men have the strength to physically abuse at a more dangerous level. The deep connection that mothers create with their newborn children and advantage in many family courts give them tremendous leverage to alienate and perpetrate emotional abuse and worse.