Donald Trump’s voracious desire for retribution has quickly evolved into a regular and predictable system. In the year since his election, the president’s rage and whims have assumed the form of policies in the same way that Joseph Stalin’s purges could be called policies. Figures within the federal system of justice who do not do his bidding are summarily fired and replaced by loyalists. Leaders who have called him to account or are in his way may face indictment, trial and punishment. Opponents have been designated under Presidential National Security Memorandum No 7 as “Antifa”: “anti-American”, “anti-Christian” and “anti-capitalist”, and...