They feel threatened by the increasing influence of minorities.... It really is that simple.. and this increase in minority control is responsible for about 90% of all civil wars throughout history in every country on the planet.
Conservative brains have more processing power within the lobe that processes fear based emotions.. the lobe is actually physically larger. Google Liberal Brain vs Conservative Brain and you can read the studies done with FMRI scans. The researchers can determine, with greater than 70% accuracy, if someone is a liberal or a conservative, just by looking at their brain scans.
The typical white evangelical male feels like he's losing his rightful place in society..... and that scares the crap out of them.
Oddly enough, most of these conservatives don't even understand why they think the way they do.