>


Basically, there's actual scientific evidence that conservative brains are physically hardwired to be reactionary

This is anecdotal, but my experiences with conservatives over the past ten years or so has GREATLY correlated with this. They just constantly bring up political discussions, unsolicited, unwarranted. You have to walk around eggshells in order to not set off the part of their brain that might remind them of some Fox News segment that told them to be mad about this or have a strong opinion about that. Any insinuation that you aren't 100% on board is met with some type of challenge, however brief in conversation.
I wonder how much of this is from Leaded Gasoline >

I suspect it's primarily from a steady diet of faux outrage pumped through right wing media channels, staring with the rise of Rush Limbaugh, etc. Basically, tilted opinion replaced fact, and the opinion was always tilted to generate anger and fear, since this always sells well and is easy to get "engagement" with.  Keeping someone in a constant state of fear and/or anxiety has long term detrimental effects on mental stability and reason. I wouldn't even be surprised if organic brain damage from constant cultivated rage can be identified. I'd love to see some studies done on this. 
It's an interesting phenomenon to watch, the crippling of a nation for reasons that pretty much amount to marketing and enhancing ad revenue.
Civilizations come and go, they rise and they fall. In the past, great nations have fallen due to war, famine, drought, and so on. We may have the honor of being the first to fall due to mass marketing.