If your company promises to give benefits to legally married couples, they have to give benefits to legally married couples.
Think of it as like making a deal with the devil. If you don’t think they are morally married, it doesn’t mean they aren’t legally married and your agreement is for married couples.
Your agreement is for what "Married Couples" meant when you made the agreement. It is not for what "Married Couples" means now that the courts have re-defined it.
As Abraham Lincoln said: "Suppose you call a tail a leg. How many legs would a sheep have?"
The man answered "five."
Lincoln responded "No, four. Just because you call a tail a leg, doesn't make it so."
Just because unelected court officials call homosexuals "married" doesn't make it so.