Sometimes it seems as if our most pressing form of pollution is cognitive pollution - people actively pumping out ideology/bias driven "research" which is either straight-up wrong or elusively wrong (wrong but protected by a whole sneak or pack of weasel words such as could be, might be, possibly, would seem, etc.)
Essentially, the authors want to create a basis for believing that people who do not share their political world view are genetically damaged in a fashion that prevents them from seeing the light. Campbell comments on the effort.
Sure, no actual scientist has found evidence for trait-based fear, but this is a humanities study, those are always engaged in an open war on science - all it takes is looking at some surveys and writing up some statistics and it feels science-y. In this case, they picked their survey targets using related people, consisting of twins, siblings, and parents and children - then they made sure to narrow the pool into a group that would give them what they wanted by 'assessing' them using social psychology tools.
Conclusion: Some people had common characteristics and therefore a genetic propensity for a higher level of baseline fear. What is this genetic propensity? Hey, that is for biologists to figure out. When the humanities try to be science-y, it's a lot like a mathematician who says he has mathematically invented time travel and it's up to those physicists to figure out the details.
The non-scientists make sure to cover themselves by saying genetics only plays a 'part' in influencing political preference - yet they don't show evidence it plays any role at all, this is just the self-recurring meme invented by people who want to pretend their cultural intolerance is evidence-based. Evidence that voting is genetic? Still none, so their desire to do more studies to show how genetic pathways influence fear is a logical fallacy.