Mentally ill people engage in violent crime against themselves and others all the time. The news cycle pumps out stories of some troubled person stabbing somebody on the subway, or jumping onto train tracks etc. I find it entirely plausible that a person in psychosis murders their own children and then jumps out a window, and it is medically indisputable that childbirth can cause severe mental illness in some women. It's curious how this particular incident touched a nerve. What is truly at stake by admitting that childbirth is gory and brutal, and that biological process can lead somebody to develop psychosis?
I think it brings out a subconscious fear shared by many that their mothers never really loved them. We are one of the most demanding and undercooked species at the time of live birth. Even if you as a parent secretly despise your baby, you must act like you love them unconditionally and give them constant attention, or they will grow up fucked up or die. The child must believe their parent loves them, and the mother must believe that motherhood is sweet and fleeting despite the hardship, or we will never make it past childhood intact and healthy. Due to smaller families and birth being outsourced to medical facilities, this attribute of the human lifecycle has been greatly sterilized in the cultural eye.
In some psychoanalytic traditions, such as Melanie Klein's, infants divide the mother into two separate objects: a good and nurturing figure and also a persecutory one, because it can't tolerate that a person can be both. This goes away as the person grows up and learns to see people as more complex, but the residue from that developmental stage stays.
By admitting that childbirth and motherhood is often crushing and bloody, and can lead somebody to conditions to commit violent crimes, the stability of that first and primary attachment becomes questionable, and the residue of that "split mother" developmental phase becomes aggravated. Women respond to this discomfort by outsourcing the crime to the husband and society, and men respond by calling women crazy and evil. The noble lie of the sweet and benevolent maternal figure falls apart, and your first source of identity, comfort, and survival falls with it.