I've known and seen lots of people refer to their partner as husband or wife even though they don't have a piece of paper that has been approved of by the All High Moral Guardians of Virtue. Similarly, I've seen people without aforementioned document say that they are married. The notion that one group of people can own these definitions or concepts is part of the whole problem.
If they are making a point, rather than just being cute, I suspect the point is that they just don't give a hoot about the whims of bigots. If that's the case, I completely agree. Bigots have held people's freedoms hostage for long enough.