There's a misunderstanding here. I'm a neo-Kantian about epistemology, not morality, so I don't think the particulars of morality are subject to a universal criterion. I'd just say that the social instinct is universal in our species, as is some set of tribal intuitions or prejudices because of how we evolved. We then struggle to reconcile those preoccupations with our history, culture, personal worldview, and so on. Whatever commonalities in morality there are would derive from the existential condition of people in nature, so I'd replace Kant's transcendental framework with some naturalistic conception of that condition.