I've been re-reading Colin Woodard's American Nations book, and this tweet reminds me what he wrote about those people whom he termed as Borderlanders: basically the Scottish, Northern Irish, and northern English settlers of Appalachia and their descendants:
"While hostile to external restraints on their behavior, the Borderlanders could be uncompromising in enforcing their own internal cultural norms. Dissent or disagreement—whether by neighbors, wives, children, or political opponents—was unacceptable and often crushed savagely."
So, see? "Cancellation for thee but not for me" didn't come out of nowhere. It has a long and rich cultural history with these people, who have been very successful exporting this way of thinking throughout a good chunk of the United States, in large part through their colonization of interior First Nations territory. I think it has also caught on with Americans who are not of that national stock because of the rugged individualism associated with them that has been romanticized as the one true American cultural ideal. IOW, people who think it makes them look cool to be rough and tough on others.