I don't think it's extreme to say that Breitbart incites hate crimes.  That's reason enough to block it from Canadian access.  Look at what happened yesterday with some kook encouraged by Trump and Bannon's hate speech to kick and verbally assault a female employee of Delta airlines who was merely sitting at her desk and doing her work with the door open.  She was wearing a hijab.  The attacker used Trump's name while supporting his attack as he made his attack.