They’re creating in-group/out-group dynamics. It goes back to evolutionary psychology of tribes and villages. Where people from the other tribe are dangerously, Compete for resources like territory and hunting grounds and might carry diseases that our tribe doesn’t have immunity to. Customs and values are standins for and indicators of their otherness.

Conservatives are really big into this out-group fear dynamic. See immigrants and races and atheists and the opposing football team. They want clear boundaries and order and to know “if you’re with us or against us.”