New Zealand officials have admitted making a mistake by allowing the man accused of killing 51 people at two Christchurch mosques to send a handwritten letter from his prison cell.

A fringe messaging board was taken down after the El Paso mass shooting, but if the internet is the modern public square, should everyone have their say, asks Dave McGinn

Far-right hate speech is much more common online than Islamist extremism, but governments and law enforcement have not policed it to anywhere near the same extent, say Sasha Havlicek and Zahed Amanullah