Don’t cry for him, Sir Keir. Argentina’s iconoclastic president, Javier Milei, has a pequeño memo for Downing Street, and it is not about long standing Argentine claims to the Falkland Islands. It has to do with the British government’s incipient crackdown on social media expression, some of which is increasingly being branded with insufficient consideration as “extremist.” Mr. Milei, never shy about speaking his mind, is miffed.