It’s an uncomfortable truth that doesn’t align with their reality. They would have to accept that they’re wrong

I disagree that that’s what’s going on in their heads. I think it’s more like being Catholic and finding out a priest is touching kids. You are able to convince yourself that that behaviour is the act of an individual, and has nothing to do with your beliefs. This is the power of religion over skepticism: it’s able to convince a bunch of people to put blinders on, and only focus on the common goal. In Set Theory terms, it lets the group focus on the intersection of their beliefs, not the union. All the good parts are where we agree, any bad parts are peripheral and irrelevant.

This is the part that “both sides” do. Like it or not, this is just inherently human behaviour.