Consider this definition of social conservatism:
Traditional values, customs and ways of viewing the world have withstood the test of time, hence they should be given deferential treatment over newer values or customs that have not survived the same level of temporal scrutiny. Moreover social change often leads to unintended consequences, most of the time deleterious ones, so change by itself should be regarded skeptically and, if deemed beneficial, should happen slowly, cautiously and methodically, so that any unintended consequences can be recognized and overcome. Finally, individual liberty is only beneficially meaningful when it is conjoined with a moral people; hence policies that promote moral clarity should be favored over those that create moral obfuscation or relativism.
Where in this definition do you see the word government power? In other words, if there is social freedom, won't the rewards and punishments of cultural markets be enough to let some behaviors/traditions “survive” and others fail? Won't cultural evolution proceed by Darwinian processes, rather than Intelligent Design (read: inculcation by bureaucrats with a bible under one arm and the Complete Works of Edmund Burke under the other?)
Customs survive or go extinct in one of two ways—either a) they’re protected by the force of powerful elites (witness slavery, Jim Crow), or b) because they ‘work’ within the environment in which they attempt to function. You may call b) relativism. So be it. But a) gets to be called “moral” by those who hold the power. It’s no different from leftish moralists with some “social justice” bee in their bonnets.
In any case: nothing under a liberty umbrella precludes social conservatism from being a personal cultural disposition that we all, as members of a free society, must tolerate -- like any other disposition or form of expression.