That's easy — Special protection from society's disapproval.
The whole point of the “gay rights” travesty is to enlist the government in a crusade to make our culture abandon its deep-seated disapproval of homosexual conduct. We can't abandon that disapproval without completely dismantling our traditional sexual morality. For millennia our culture has taken for granted that sexual expression is to be celebrated only when it serves the purpose of creating and sustaining a family in the context of a monogamous marriage. That idea is a large part of what we are and a critical element of our culture's fabulous success.
You don't make government smaller by empowering it to rip that idea out by the roots. You make it larger and more repressive. Government will have to police speech and social relations in highly intrusive ways as it tries to revolutionize the West's mores. That, of course, is the antithesis of limited government.
Nobody who wants the government to revolutionize our culture's morality is a conservative by any definition. You can certainly be gay and conservative, just as you can be a conservative adulterer. But you can't be conservative and still agitate for the government to promote acceptance of homosexuality. The iron law of contradiction forbids it.
You’re thinking is twisted. You make the government smaller by reducing what it does to that which the Constitutions says it may do. period.