Glenn Greenwald says a lot of cringy libertarian shit but this isn't one of those instances. It doesn't make the truth any less true just because who is saying it has dumb, awful opinions on other things.

It'd be weird as an investigative journalist supportive of whistleblowers like him not to be in favor of free speech. He recently talked about Russel Brand, apparently not a leftist anymore as well according to some people.

People here may disagree, but in an ideal world, fascists or capitalists should be allowed to debate because in these ideal conditions their falseness would be efficiently deconstructed, the public failure of their arguments would serve as a useful reminder for the rest of us.
In my opinion, the u.s.s.r. would have made a mistake by banning anti-communist parties in this ideal world ; however, in the real world, such foreign agents would have perhaps been too powerful/financed/'able to corrupt', the u.s.s.r. already had enough vital threats to survive through in its first decades. If they enabled the conditions for an ~annual debate repeating the demonstration of the errors of capitalism, including with western authors, that would have been beneficial for them(, i'm aware that reality is more difficult, it's just a thought).