There is a certain type of Righteous Man(tm) that seems almost obsessed with homosexuality. They want to keep it out, out OUT of every institution, out of society if possible.
Common wisdom says the average homophobe is hiding his own gayness, trying to make society hold the closet door shut for him.
I have a different notion.
These Righteous Men(tm) know they are sinners. They know they are coveters and adulterers (if not actively then in their hearts or by marrying divorced women), they know they are murderers (if only by virtue of hating).
But they are not gay.
Gays are the one group they can truly feel morally superior to. And like every privileged group, they want to retain what little sense of moral superiority they have.
As the Gay Rights movement gains steam, and society says there is no need to consider the QUILTBAG less moral than others, they will shout all the louder, trying to retain that one area where they feel superior.