In 1998 – the year I started at university – the columnist Peter Hitchens was invited to speak at an NUS debate about cannabis. Half way through, the chairwoman told him to leave. Some students, she said, had objected to his “offensive remarks”. Amazed, he asked what remarks they meant. He wasn’t told. His microphone was switched off, and the president of the NUS ordered him out. The next day, the NUS issued a statement deploring Mr Hitchens’s supposed “implication” that he was “proud to be associated with sexism and homophobia”.