I do understand there are some mores (or taboos) that we commonly will find a rationality for, even when there isn't a logical reason for it. A big one is the emphasis of high-contact sports programs in our education system. A lot of lives get ruined (and a few ended) every year to gridiron football injuries in the US, and yet it is difficult to imagine ending football programs in our high-schools and colleges (even if to switch to sports that involve less risk).
There was a study about instinctive mores, featuring the story of Julie and Mark (an adult sister and brother who go camping, have sex, decide not to do it again, but are not harmed by the encounter), and not only did subjects assert such a coupling was morally wrong, but would seek out reasons to justify their belief, even if it didn't fit the specific circumstances. Similarly, it's a common assumption that gay sexual relations between relatives is taboo, even though the commonly understood purpose of the proscription (to avoid conceiving children with birth defects) is not actually possible in the relationship.
For this reason, some social problems that exist (such as the social isolation of boys and young men that puts them at risk of turning to the alt-right) that we are disinclined to address (I've heard the sentiment before: sure, they're suffering, but fuck those guys ) because we have a collective drive to see those issues in a specific way, such as holding contempt for teenage boys as a demographic, even when we know it will drive them into organized hate groups.