Polygamy is the logical next step from this statement. Since Massachusetts is the battleground (U-Boat Teddy's involvement) and unitarianism is big in MA compared to other areas of the USA, it will be a short time before polygamy is brought before the Supreme Court of MA and accepted.
The left is playing a shell game. While the conservatives wait years in committee for passage of an emasculated edicts, marriage protection amendments, and the like, the courts will allow everything not spelled out exactly in the MA constitution.
The left is using the constitution against the constitution both in the states and at the federal level.
Meanwhile, each decision stirs up debate which brings the activities into the mainstream consciousness. Someone uses Roman law over biblical prudence in an argument and BOOM: Instant tolerance. Add the fact that people tend to stay away from arguments in a letigious society and you have acceptance protected under the canopy of defacto rule.
A conservative might not be in favor of state-sanctioned relationships at all. Do you realize that if you can pass an amendment saying marriage is between a man and a woman, you can pass one saying it isn't?