On one point, I believe you're mistaken.
Libertarians do believe in generally accepted moral principles.
The belief that any act that infringes on the rights of others should be prevented is a principle tenant of Libertarianism. This covers many generally accepted morals such as a belief that murder, rape and theft are wrong. Many conservatives believe that they know what is best for everyone's private life and that people should be forced to abide by those beliefs. Libertarians tend to believe that people are entitled to differing lifestyles, even if they find them abhorrent, as long as it does not infringe on the rights of others. You're risking mob rule.