And now for my serious take... I don't think libertarianism and religion are mutually exclusive, but I do think many particular religious beliefs are incompatible to one degree or another. If you think your religious beliefs should be enforced through force, you are not libertarian - your liberty philosophy has a blind spot. I think that is why I have found a shockingly (to me at first anyway) number of atheists in the LP. I have been to 2 state conventions and 1 national. A notable exception would be most of the people who voted for Bob Barr to be the LP nominee, mostly from Southern states. (I voted for Mary Ruwart right up to the last ballot despite the outlandish child molestation mudslinging campaign.)
I even find many of the people attached to the Ron Paul campaign to be unlibertarian because of this blind spot if you will. I was a huge Ron Paul supporter and still am given he is light years closer to true libertarianism than his closest Congressional member rival. I disagree with him on abortion, and my big beef with him there is his disrespect for his own condemnation of commerce clause abuse when he voted for the partial birth abortion ban. But that's a constitutional issue, not libertarianism per se. When it comes to immigration, I think he could be more libertarian even considering the pragmatism of border protection until we get rid of the welfare state.
But after the primary was decided, it seemed those who hung onto the C4L/Ron Paul movement around here anyway were more John Birch and Constitution Party than libertarian. They believe in God, Country and the Pledge of Allegiance in that order. They don't mind exercising a little uninitiated force when someone shows disrespect for their guy in the sky or the star spangled banner. I find that mindset disgusting. They aren't content to let gay people be equal citizens and they usually have a hard time with legalizing drugs, especially the non-pot variety.
I've had more than one person noting my atheist and libertarian viewpoints say something like, "You just don't like anyone else telling you what to do." and I would say they are very right about that.