At Cambridge University I was taught a laudable method of argument: you never personalise, but you have absolutely no respect for people’s opinions. You are never rude to the person, but you can be savagely rude about what the person thinks. That seems to me a crucial distinction: people must be protected from discrimination by virtue of their race, but you cannot ring-fence their ideas. The moment you say that any idea system is sacred, whether it’s a religious belief system or a secular ideology, the moment you declare a set of ideas to be immune from criticism, satire, derision, or contempt, freedom of thought becomes impossible.