‘A lie will gallop halfway round the world before the truth has time to pull its breeches on.’ So said Cordell Hull, President Franklin D. Roosevelt’s secretary of state, long before the internet. Now we live in the virtual age. What’s true is barely relevant. No sooner has a man shot 10 people dead and been taken into custody than his suspected motives are shoved into the great culture-war grinder and splatted out of a million social media accounts.