As usual the media gets it wrong again (and again and again). They love to pronounce that libertarians tend toward the liberal side on social issues. They especially like to say that libertarians support LGBT marriage.
The fact is that libertarians are opposed to the government regulating marriage at all, for anyone. Saying that is the same as being pro LGBT is incorrect at best and flat out lying at worst.
In fact, most libertarian minded people will tell you that they couldn't care less what any given persons sexual preference is. That is each person's own business and is really only secondary at best in the issue.
The problem is that the folks in the chosen opposing two party sides want any ally they can find to push their own agendas.
Actual libertarians (not party Libertarians, those are a different animal) are supporters of individual liberty AND individual responsibility.
A libertarian is opposed to the government regulating or influencing anything that infringes individual liberty. That's it.
Some individual libertarians may personally support specific issues, but libertarianism in general doesn't pick sides in regards to social issues and political party agendas.
The sole concern is keeping government, religious and social groups from infringing on individual liberties.