Libertarianism is a philosophy that holds that government involvement in anything is always a bad thing. Agree with it or not, it leads inevitably to a clear and specific set of principles--social issue stances that generally qualify as "liberal", economic stances that generally qualify as "conservative". It's not directly a one-to-one mapping in either case, but there is a usual reticence among libertarians to allow any quarter for government, aside from maybe busting counterfeiters or things of that nature.
So, when one considers the Ron Paul philosophy, one naturally needs note that it bears less relation to the classical conception of libertarianism and much more of a semblance to the modern conception of conservativism in every way aside from on foreign policy. From my vantage point, it seems to me that Ron Paul has few hangups about curtailing reproductive rights or gay rights, that he's all too willing to massively increase the federal government's power viz. border control, and that he's all too willing to curtail free trade by stepping up governmental involvement in the global marketplace. Some might say that these issue stances are correct, and that may be true, but it is also irrelevant. It shows that Paul is a libertarian in the same sense as I am one--which is to say, not at all. Sure, I have some libertarian leanings, but everyone has libertarian leanings of one sort or another. Just like we all have authoritarian leanings of one sort or another. I just wish Ron Paul's acolytes would admit that he's on the same scale as everyone else, rather than as some revolutionary freedom maximizer. He does want to maximize freedom in some areas, and he wants to minimize it in others, just like everyone else does. That makes his claim to represent freedom just as strong as mine. We can debate differences on that playing field.