Well, there are a bunch of issues coming up here.
First, I doubt that anyone here, including Dale, belongs to "a church that encourages homosexual sin." Perhaps the Cathedral of Hope encourages behavior that strikes another member as sinful. But, bluntly, that is a highly judgmental way to attribute it. I notice the member in question belongs to what some people I know would describe as a Baptist "church" -- which in their opinion, having not placed itself under the authority of a bishop ordained in the apostolic succession, has no right to consider itself a church. Bottom line: personal views on morality or ecclesiology do not mandate legal action against them.
Second, about the Constitution. A. There is no provision in the Constitution regarding marriage. B. The Tenth Amendment provides that whatever authority is not delegated to the Federal government resides with the states. So it is up to them to decide what does and does not constitute a valid marriage.
By the way, I find it really offensive that some Christians believe that Rachel bore Joseph and Benjamin out of wedlock. And the assertion that God only accepts the marriage of one man and one woman means that you have just called Jacob's and Rachel's relationship not a marriage and those two patriarchs illegitimate (I think the board's software will censor out the proper technical term).
In my mind, individuals may certainly consider the covenanting of two men or of two women to each other as "not real marriages" -- but I feel that it is not their privilege to legislate that into law. It would be unfortunate if someone decided that marriages presided over by Catholic priests or Methodist ministers were invalid, on the basis of their own beliefs. Applying the Golden Rule, what people are doing here is no more than the same thing -- what X and Y believe to be a commitment to each other in marriage, "really" is not because of their own beliefs.