Except it is true about social liberals.
You don’t know that social liberals are the back bone of liberalism, of the voters for the Democrat party and it’s agenda?
You don’t know that social conservatives are the back bone of conservatism, and the right?
No, I don’t know that. I have seen the assertion (and with it the assertions implicit in replacing “libertarian” with “social liberal”), but have not seen any proof. Just a lot of noise and chest thumping about it, as if saying it often enough makes it true.