Personally, I'm insulted when someone says libertarians are socially liberal. They don't mean socially liberal in the classical sense, but in the modern sense and I have just about nothing in common with modern liberals. They approach every topic from a different angle than I do and with different goals to reach. They view rights as a gift from the state and liberty as simply permitted. I'm the exact opposite on both positions and so when I find myself agreeing with them on a general idea, lets say gay marriage, the ends are different and the reasons they have for their position are usually things I reject. The basis for their position is regularly equality, but I view the idea we shape policy around equality outside of liberty as idiotic and dangerous. My view is simply liberty and the right of all people to marry who they please. I have no use for equality arguments built on marriage benefits or some hair brain idea of approval by the state. Liberty offers equality and so further attempts past that point are baseless, unwarranted and almost always violating the liberty of someone else to obtain. I have no use for modern liberals. Their ideas of social freedom almost always involves coercion or direct involvement by the state in our lives. My idea is fairly simply really. Allow the liberty and call it done. We don't need modern liberal ideas of equality to muddy the waters.
Liberals as we know them today are not for freedom and when they talk of it you can always be assured that government is going to play a part in whatever plan they have towards it. That is not freedom, it's government control of freedom.