That's a good point. I like this analogy.

One fish says to another, the water is warmer today. The fish replies, what's water?

Most people are more practical and less abstract. Most are less curious than those that tend to align with the liberty movement. This is my experience at least and after reading "The Righteous Mind" I think it is something we are born with.

I've also noticed that people react to being questioned differently. If someone asks me a question I don't have an answer to or haven't thought of I tend to enjoy it. I will reply that is interesting, or I need to think about that. But most people I know do not react this way. Some get defensive and will really make fools of themselves. I usually just let it go and consider them unequipped for deep conversation. Others just shut down like you describe. I find that these people just change the subject. They either aren't interested in the unknown or new, or they feel insecure talking about things they haven't been trained in.

The vast majority of people I have interacted with in my life are like the person you know. They just repeat what they have been trained to think and when confronted with evidence just get quiet. Its kinda sad to me.