Universities are bastions of free speech and incubators of new and challenging ideas. But sometimes they fail to see the creeping extremism on their campuses. When David Irving goes to a university to deny the Holocaust – university leaders rightly come out and condemn him. They don't deny his right to speak but they do challenge what he says. But when an Islamist extremist goes there to promote their poisonous ideology, too often university leaders look the other way through a mixture of misguided liberalism and cultural sensitivity.