Bigotry has been a big part of the Moral Majority's platform for decades for a reason - it works on that demographic

I have an armchair theory about one possible contributing factor

These are two of the most fundamental beliefs of evangelicals and they don't make much sense when you put them side-by-side:

1. God is the ultimate progenitor and prototype of love

2. God wants to torture a LOT of people forever, some of whom you may know personally and may be all appearances be decent people

This creates a certain amount of cognitive dissonance

Rather than reconsider those beliefs (which may result in your own everlasting torment), it's far easier to resolve that discomfort by dehumanizing non-Christians. Maybe they're actually really rotten people that deserve to be tortured