I did not think this was a substantial argument. You deftly pointed out the holes in it. It is the only possible secular one I could come up with. I am more inclined to agree with what C. S. Lewis said in his book “Mere Christianity” (paraphrasing here). We need to have a seperate institution for recognizing the relationships of those who do not believe in God and the principles held in His word. I do not understand the lifestyle of homosexuality, how could I? I do see the need to somehow protect the rights of those few individuals who live a monogamous homosexual lifestyle, calling their relationship a marriage is not it, however.