Earlier quoted context omitted.
> I think the biggest contributor is just that left-leaning people are more likely to be offended by right-leaning views. More likely to have empathy is another way to phrase that.
You can be super emphatic an right wing, how do you think someone becomes a populist nationalist. Besides from a European perspective even someone like Obama or even more obviously Hillary (based on the amount of war mongering she has done alone) is center or ultra right.
At the bottom? Fear of the other; in the United States, fear of the other rooted particularly in racism. Because it's not "nationalism" here--a disease by itself, but a controllable one. It's white supremacism, given nicer clothes by calling it "white nationalism" for some godforsaken reason, peddled by leaders who want the bottom to vote their way. It's not like it's news. Lee Atwater pegged this whole disgraceful thing decades ago. To legitimize and get boots on the ground for economically regressive policies, the right wing of the United States leveraged this racially-motivated insecurity; now the racist tiger has eaten them and they are so very surprised that the racist tiger was racist all along.
At the top? They're the ones doing the peddling. Some is surely true-believer racism. Some is also surely cynicism--because the bottom will eat it up and there's your leash to drag them where you want. It isn't exactly complex.
(And, no, Obama and Clinton are not "ultra right" from a European perspective; that's the sort of mendacious both-sidesing I expect out of actually far right speakers, though. Obama and Clinton would be generically center- to center-right politicians on a Europe-calibrated axis. The modern Republican Party is more like Ukip.)