Probably that many people are like exclusively emotion driven. I don't think we should all be like purely logical Vulcans. Emotions are very fast and can be a good survival tool. Like if you're waiting for the train and a bear wanders onto the platform, you don't need to wait to logically evaluate if it's a threat. Just run.

But people rely on emotions for everything. We all do this. So you have like someone telling you something factual and uncomfortable, and you just reject it.

"Eating meat is bad for the environment and is cruel to animals. We should all eat a lot less meat" makes a lot of people's emotions flare up. The facts don't matter. They feel like they're being insulted, that the other person is a blowhard, blah blah blah.

The oatmeal did a comic about this, actually: https://theoatmeal.com/comics/believe

I think this is why we can't have nice things.