The conservatives have taken it over. Moderate and liberal Republicans barely exist anymore as they can't win Republican primaries because conservatives make up a supermajority of the Republican base and that trend has only been increasing:
http://www.gallup.com/poll/148745/political-ideology-stable-conservatives-leading.aspxLiberals and conservatives are on opposing sides of the political spectrum. Does that mean that they each have just as good rational justifications for their positions? No.
Fiscal and social conservatism is not compatible with rational thinking. It's just more false equivalency fallacies to say that liberalism and conservatism are both right. Conservatism is irrational, liberalism is not.