When Manchester United told their 66 million Instagram followers on Saturday they had lost 4-2 to AC Milan, the responses were pretty unequivocal. The kinder supporters wrote about a “reality check”, or implored the club’s deeply unpopular owners to put their hands in their pockets. In one case, the Glazers and their co-owner, Jim Ratcliffe, were told to “sell the whole team”. Others used terms like “disgrace”, “disaster”, “embarrassing” and “terrible”. “We are cooked, [head coach, Michael]...