We lost. Time to wave the white flag (or the rainbow flag, I guess).
Yup. A really big part of the issue is that, as Toqueville pointed out, is that Americans worship public opinion. We have a tendency to decide that whatever most people believe in is what is right and moral.
This means that until recently most opposed homosexuality primarily not because of deeply held moral beliefs, but because that was the popular belief. Now most of those same people switch sides as the popular opinion changes.