The email newsletter service Substack is facing a user revolt after its chief executive defended hosting and handling payments for “Nazis” on its platform, citing anti-censorship reasons. In a note on the site published in December, the chief executive, Hamish McKenzie, said the firm “doesn’t like Nazis”, and wished “no one held these views”. But he said the company did not think that censorship – by demonetising sites that publish extreme views – was a solution to the problem, and instead made it worse. Some of the largest newsletters on the service have threatened to take their business elsewhere if...