“Love thy neighbour” and “live and let live” are also biblical themes. I could go on. We pick and choose those we wish. The world is moving on from fear of (what is a biological) difference to tolerance to, slowly, understanding that difference and respect are two sides of the same coin. There are so many more important problems in the world that to worry about two people in love wanting the right to get married and have (or adopt) kids.That seems to me to be the pinnacle of responsible behaviour.