The expanding legalization of same-sex marriage in the Western World may pose significant challenges for the relationship between many religious and socially conservative marriage and family therapists and their professional associations. In the present analysis, I look to the field of moral psychology, particularly Haidt's Moral Foundations Theory, to provide greater clarity regarding the nature of this tension and a resultant tightening of the boundaries of acceptable diversity that could ensue. I then outline some concerning indicators from mental health associations relative to their potential willingness to tolerate conservative perspectives in meaningful ways and identify some specific areas of possible tension for conservative therapists trying to integrate their deeply held moral values into ethical practice with same-sex couples, with a specific reference to the viability of “conscience clauses” and values-based referrals. I conclude with some recommendations through which the field of marriage and family therapy can reduce the potential for conflicts and thereby reassure these clinicians that they continue to be welcomed even if their vision of marriage differs from that which is formally endorsed by their professional associations.