The Wireless Festival was cancelled this week after its headline artist, Kanye West, had his entry clearance to Britain revoked. The government’s position was that his presence was not “conducive to the public good”. Not surprising. But not uncommon either. Over the years, plenty of controversial figures have been kept out of the UK on broadly similar grounds. Geert Wilders, the Dutch politician, was refused entry in 2009 over fears his anti-Islam rhetoric would threaten public order. Zakir Naik, an Indian preacher, was barred the following year after he made remarks on Osama bin Laden that were seen as supportive...