"Joseph Smith, a single man and Michael Smith a single man." That would be a daft way of putting it, because they aren't "single men" - they have entered formally into what in the UK would be called "a civil partnership". Something of the form "Joseph and Michael Smith, civil partners" would be a far more appropriate way of expressing that in this context.

It's not really analogous to the racial/racist use of "separate but equal", because that was about pretending there was a difference where there was no relevant difference whatsoever. If it were a question of asserting a difference between gay men and straight men, or lesbian women and straight women, in order to justify treating them differently as individuals, the analogy would indeed be fair - however that's not what is implied.

The point is it can be reasonably argued that there are differences between the relationships which can justify using different names. That's what I meant by the analogy of baseball and cricket or beer and cider.

It could well be that the popular definition of the word "marriage" might change over time, to include both kinds of relationships. That would be the time to change the dictionaries. In the meantime the task of bringing the USA into line with other countries where civil partnerships and marriages have equal legal status should not be delayed by treating the issue of the name as crucial, and it does soudn as if this could well happen.