Simple. Right-wingers tend to occupy the middle of the intelligence spectrum while left-wingers occupy the lowest and the highest (at least Democratic voters as a whole; many of the less intelligent Democrats don't understand liberal vs. conservative). However, the lower-middle end, in which many of these comments are from, is generally more conservative (note that Atlas, both left and right, is at the upper end of intelligence).
You're mixing up intelligence and education. They are far from the same. And political morons aren't necessarily unintelligent, they just think with their platforms and not their good sense. For example look at some of these ridiculous protest groups on elite college campuses. Any coal miner or hick on a tractor will be able to tell you that divesting from hydrocarbon companies won't make a difference in the environment as long as people keep using the fuel - just as soon as you tell them what divesting means.
