I'm a Republican and I'm certainly not a fundamentalist or extreme. You're just making bare assertions, without backing them up. Most republicans elected to office are moderates, so I'm not sure where you get this extremism thing from. Most Democrats elected to office are also moderates and it wouldn't be fair to call them extreme either. This is why no matter what your political ideology you always feel like whatever candidate your party elects is fake. There are some exceptions, such as areas heavily dominated by Democrats or Republicans, but we should leave the anomalies out of this discussion.
The republicans certainly have a fairly large Christian base they must pander to, but their policies are largely free of that type of influence. I think there is a tendency to see anyone you disagree with as extreme, but take a close look at different party candidates sitting in the exact same seats and you'll see a lot of crossover with concern to their political ideology. Bush's policies were largely similar to Obama's.
I would say right the Republican party is definitely more extreme and ideological than the Democrats who are more pragmatic. Hence the term "RINO", Republican in name only. Then there's a course the Tea Party movement, shutting down the government, threatening to default on the debt, etc. Both parties are more partisan now then ever largely due to the primary system and how the districts are draw, where Republicans only worry about primary threats from the far right and not the general election and Democrats only worry about primary threats from their left and not the general.