There are the needs of communities and institutions. And sometimes they necessarily constrain individual liberty. This all goes to the fact that there' s room for debate. As any pro-life libertarian will tell you, there are good arguments to be found among the libertarians, just as there are good arguments to be found within the conservative movement. And that is a wonderful thing.
Arguments offer insight.
Arguments are necessary because not every event presents itself in an ideologically consistent and digestible fashion. Sometimes it is a noble thing to conscientiously refuse to enlist in a war. And other times it is cowardice and treason. The trick is to figure out which is which, and the only way to do that is have people of good will disagree with each other. Libertarianism is an intellectual acid test for conservatism.