It's actually normal for people to be cruel and vindictive toward people they perceive to be moral abominations. They don't deem such people to be "human" and a member of their tribe. Americans have a
very sour opinion of their fellow citizenry that is highly unusual compared to other OECD countries. Some of it has to do with politics, but the root of the problem lies with Americans having a weak sense of self relative to one another. The reality is that large swathes of the population across the political spectrum see their peers as subhuman, are baffled by what motivates them, and take great delight in screwing over their fellow countrymen.