Thank you, thank you, Timothy Taylor, for introducing me to the work of John Tooby and Leda Cosmides. (Check out Coalitional Instincts and Fox News, or MSNBC.)

We are evolutionally programmed to join coalitions and those coalitions ask us to signal our loyalty to the group. Sometimes they ask us to do despicable things. 

Conversable Economist: How Coalitional Instincts Make Weird Groups and Stupid People, 2018-Jul by Timothy Taylor

…we all feel a strong need to join groups, we do have some degree of choice and agency over what groups we end up joining. Even within larger groups, like a certain religion or political party, there will be smaller groups with which one can have a primary affiliation. It may be wise to give an outlet to our coalitional nature by joining several different groups, or by pushing oneself to occasionally phase out one membership and join another.