Let's step back.
It's likely that humanity has evolved to have people with liberal and conservative minds in any given society. According to mounting psychological research, liberals tend to be open to new experiences, while conservatives seek to protect what they already have. Often these mind-sets result in political clashes. But the tension between liberal brains and conservative brains makes sense for survival. There are times when it's important to discover new things, and there are times when it's important to avoid dangers. The tension between those two strategies is what has fueled human political conflict for millennia as groups argue over how a society should be run. But it has also kept us alive.
Through this evolutionary lens, conservatism is a strategy to protect a society from harm from both outsiders and diseases. Ebola hits this exact conservative nerve—it's a deadly disease from a foreign country. Ebola is activating all the evolutionary alarms of the conservative mind.
John Hibbing, a leading researcher in political physiology, explains it like this: "What we've found is pretty clear and consistent—that conservatives tend to have more reaction to negative things. We like to see not just if they report in a survey-type format whether they are bothered by that, but actually physiologically if there has been a change."
In his experiments, Hibbing often attaches electrodes to liberal and conservative participants' skin and then shows them disturbing images, such as a man eating a handful of worms. In these tests, conservatives sweat more (i.e., have a stronger gut reaction) in response to the disgusting stimulus. And when Hibbing hooks participants up to eye-tracking machines, he finds conservatives monitor more closely the things that make them squirm. So they are more readily provoked and more vigilant. These differences between liberals and conservatives are likely deep seated in the brain: scientists have found that conservatives tend to have larger amygdala, a region of the brain involved in fear processing, than liberals do.
And when people become fearful, they're more likely put distance between their group and others. "Since out-group members are more likely to carry pathogens to which members of the in-group have not yet developed immunity, avoidance of out-groups can be adaptive when the threat of the disease is salient," UCLA researchers wrote in a 2006 paper.
In that paper, the researchers found that when participants were primed to think about disease, they "increased their preference for the American over the foreigner and increased their attraction to the American." They became less receptive to outsiders, just like certain politicians seem to be doing right now in the wake of Ebola.
"It doesn't mean that conservatives are deeply flawed," Hibbing said. "From an evolutionary point of view, responding to negative things in the environment makes a lot of sense. You need to be aware of them."