There are many sane Republicans...unfortunately, the leadership and vocal element is allowing the party to be defined by this lunatic fringe. I've always thought most Democratic Representatives were a bit skewed and moon eyed in their pronouncements, but when compared against the likes of Michelle Bachmann, they look academic and positively benign.
The key difference for me in this topic is that with Democrats, you know you're going to get social programs, tax hikes and an increase in the size of government. They tell you that up front. With Republicans, you get lied to during the campaign....and then end up with the equivalent of Democrats in office. That dynamic is what makes this current 'tea party' movement so transparent and false. These people aren't interested in changing the system, or fulfilling the platform promises....they are only interested in voting their party back into office.
If you want to retain the status quo and keep this nation stagnant, fine. But at least be honest with the motives of issues oriented groups....from both parties.