The study is seriously flawed. There are a large number of possible things that could differ between a group of college-age liberals and college-age conservatives, and any of those things could be the real reason their ERP measure differed between the groups. That ERP measure is larger in people who are depressed or who have obsessive-compulsive disorder. It is smaller in people who are impulsive, aggressive or antisocial. It is also smaller in people who are drunk! The authors didn't attempt to see whether their groups differed in any of these other ways. If they had bothered to do a careful study in which they controlled for other possible influences on the ERP, they might have found no difference or even come to the opposite conclusion. But, it's a lot easier to make a big splash in a press hungry for big splashes than it is to do careful science.