I think it's more prevalent among republicans because, on the social conservatism front, they're constantly swimming against the current of progress. Social conservatism is built around winning battles but losing wars, and eventually people who see this happen often enough decide not to concede, but to stage their last stand at the alamo. That they're still failing in a lot of ways (not likely to win in 2016, for instance) is infuriating to their base.
I think democrats are less inclined to attract ideologues because the tide of public sentiment tends to sway in their favor over time, thereby abating some of the need for extreme measures. For democrats, their rallying cry since 2008 has been that progress is happening too slowly. For republicans, it's that progress (their idea of it) isn't happening at all. In a republican's mind, they see that we live in a country where women can serve in combat roles in the military, gay people can get married, we're practicing diplomacy with Iran rather than bombing them, health insurers can't discriminate against those with pre-existing conditions, etc and see a country that has been completely overhauled by liberal ideology, even if it only feels like incremental steps toward ideal solutions for most of us.
