[we should do so]
Even those gays who do not engage in Sodomy are still prohibited from marrying each other. This is because, as the Rema mi’Panu records [3:21], there is even a prohibition for Noachides merely to draw up marriage contracts for homosexuals [Chullin 92a-b] [Bava Metzia 75b] this passage to prohibit causing a person to be in a situation in which he is likely to transgress a commandment. In addition, it is clear from Tosafos (throughout the first perek/chapter of Avodah Zarah) that this rule (of not causing others to sin) applies even to a Noachide.