I can see where you are coming from, but I have to defend Paul on this. If he did stick to his ideals and ran for the Libertarian party, in all reality there is no way in hell he would have any chance to win the Presidency, which is only slightly worse than his long shot now. (Odds are at 7-1, if you were curious.)
Anyway, there is not a SINGLE politician in Washington DC who is completely blameless and always, 100% of the time sticks to their ideals. Ron Paul seems pretty damn close to me, but you can't blame him for running Republican. If he didn't, he would be basically a non-factor and we would be stuck with only good ol' Giuliani, McCain, Brownback, and the whole gang. Instead we now have a radical new candidate who is stirring things up and creating a chance for real change. I would rather have being somewhat misaligned in party choice than being a complete non-factor.