I don’t believe that conservatives or Trumpkins suffer, for the most part, from some empathy disorder. There's a discussion of Corey Robin's book up at Crooked Timber in which there are many mentions, among the commentariat, that the Right is just a mass of moral failure, built on a deeper emotional deficiency. I don't think this is true, or, more to the point, that there is any evidence for it.
So what makes for the visible lack of empathy among conservative groups for certain groups? I would look for the way empathy gets into our social action more than for how our neurons work, here. A neural interpretation of ideology might seem real scientific, but it is no more scientific than, say, an atomic view of ideology. It is reductionism in a void - the void being our vast, vast ignorance about how evidence of our neural processes actually work on the higher level of personal and social interaction. Instead, we read backwards, from those interactions to the neural maps. What seems like science is actually slight of hand - the kind of thing that impresses New York Times op ed editors.
I'd propose, more modestly, that there is a difference in the way distance is interpreted. There’s a famous essay by Carlos Ginzburg, Killing a Chinese Mandarin: The Moral Implications of Distance, in which he explores the background to a famous scene in Pere Goriot – the one in which Vautrin proposes (in a sort of colonialist koan} to Rastignac the following thought experiment. http://elplandehiram.org/documentos/JoustingNYC/Mandarin_Distance.pdf Ginzburg If you could gain a fortune just by wishing the death (a wish that would be effective) of a Chinese mandarin half way around the world, would you do it? The point is that distance – and the way we make distances, geographically, ethnically, economically, sexually, etc. – has a global effect on our moral sentiments. I would say that the distance making in the Trumpian era of conservatism is going back to an earlier form of it, at least in the U.S., which last became this virulent after WWI.
Interestingly, the symbol that Trump wrapped his campaign around is the “wall”, this mythical distance fixer that would forever separate white “authentic” America from Mexico (the brown mixed America, I guess).
It isn’t as if liberal culture doesn’t deal in distance as well. When HRC (and I voted for her, in spite of this) ran as a vaguely feminist politician, she never spoke at all about why, then, she would have ended her days in the state department signing off on appallingly large arm sales to the Saudis. Imagine a politician in the 80s running as a civil rights candidate and at the same time offering major support for the Apartheid South African state. But I think this was another case of distance – both geographical and cultural – that simply excluded Saudi women from the moral consideration that one would give American women.
I’m not sure anybody is a master of the moral distances we exist among. I’m not. So I am not saying I understand how to counter distance effects. I’m just saying that they have to be read into the narrative of our political ideologies in order to understand them.