Suppose for a moment, that we define a virtuous act as bowing in the direction of Mecca every day at sunset. We attempt to persuade everyone to perform this act. But suppose that instead of relying on voluntary conviction we employ a vast number of police to break into everyone's home and see to it that every day they are pushed down to the floor in the direction of Mecca. No doubt by taking such measures we will increase the number of people bowing toward Mecca. But by forcing them to do so, we are taking them out of the realm of action and into mere motion, and we are depriving all these coerced persons of the very possibility of acting morally. By attempting to compel virtue, we eliminate its possibility. To be moral, an act must be free.
Murray N. Rothbard, "Frank S. Meyer: The Fusionist as Libertarian Manquè". Quoted in Freedom and Virtue.