There are several issues at play here. First, we must separate the "agenda" from the equation. I think it wrong to deny a couple, hospital care and decisions because of a lack of a legal "commitment" . On the other side of the coin, the issue of child-rearing is still prescient. Should a gay couple be allowed to adopt? create children, through IVF or as sperm donors? Again we allow people to procreate, even though they may be pre-disposed to certain abnormalities or diseases. Of the 6 couples I know who have been together over 45 yrs, 3 are G.
As for allowing society as a whole to determine what is right or wrong, has some definite drawbacks, slavery, French Revolution, Russian Revolution, Holocaust, are examples of the those "drawbacks".