Libertarians usually claim that anything that is consensual ought to be permitted by law.
But some of them go beyond that, and claim that anything that is consensual is moral. That, I think, is an obvious mistake. In a Facebook discussion, I just offered the following example: A drunk who is killing himself with liquor and his enabler may, fully consensually, have the enabler supplying the drunk with oodles of liquor. While I would not want this made illegal, I have no problem declaring it immoral.