Lack of empathy is definitely aided by ignorance, but there might be some kind of critical period in development when children really benefit from examples and reinforcement of empathy.
Republican style conservatism draws such tight borders (walls?) around potentially sympathetic humanity, that even being American isn’t enough.
Can’t be:
Black, brown, yellow, anything except white or orange
Jewish, Muslim, Hindu, Buddhist, anything we haven’t heard of
Atheist
Liberal (progressive is bad too because we hate both liberty and progress)
Feminist (Being female is bad enough, you don’t have to go and respect yourself)
Well-educated (or hide it well)
Foreign (Brits are acceptable if they yell on fox news)
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Sorry for going on and on, wrapping up
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TL;DR
They give impression they want to reduce legitimate humanity to a tiny circle.
Their policies promise to reduce us all.