En 2004 la reverenda unitario-universalista Debra Haffner del The Religious Institute on Sexual Morality, Justice, and Healing publicó "An Open Letter on Religious Leaders on Marriage Equality to affirm same-sex marriage from a multi-faith perspective" ("Carta abierta a los líderes religiosos sobre la equidad matrimonial para apoyar el matrimonio homosexual desde una perspectiva multi-fe").