At least three mass shootings this year — including one in El Paso — have been announced in advance on the online message board 8chan, often accompanied by racist writings. We look at the battle over shutting down the site. Guests: Kevin Roose, who writes about technology for The New York Times, spoke with Fredrick Brennan, the founder of 8chan. For more information on today’s episode, visit nytimes.com/thedaily.  Background reading:Fredrick Brennan started 8chan as a free speech utopia. But the site became known as something else: a megaphone for mass shooters, and a recruiting platform for violent white nationalists.Several tech providers pulled support for 8chan, temporarily taking the site offline. The decision to do so was not a straightforward one for the security company Cloudflare.