Of course he goes on Tucker Carlson's show, because stories like the Hunter Biden laptop were suppressed by CNN, Facebook, Twitter and others. In fact they were called "Russian disinformation".
Now in 2022, many of the same outlets suddenly acknowledge the authenticity of the story. CNN has James Clapper as its own security analyst (https://en.wikipedia.org/wiki/James_Clapper#CNN_national_sec...), why would Greenwald appear there after all that has happened in 2013?
Many of Greenwald's "conspiracy theories" are facts two years later.
Greenwald (and Tulsi Gabbard) quoted Nuland directly, who admitted that there were biological research labs.
Greenwald had previously worked on the Anthrax story of 2001, where a couple of high profile people got sent a sophisticated Anthrax variant in the mail.
It was supposed to be foreign terrorism at first, later it was found that the strain came from a U.S. research facility.
Biological weapons aren't allowed by treaty. Research how to combat biological weapons however is allowed. So many countries produce strains in biological research facilities under the guise of defense.
That is precisely Greenwald's point, he has never claimed that bioweapons are manufactured in Ukraine. He has claimed that dangerous biological agents might be present, like they were in the U.S. in 2001.
It takes a lot of history and reading to understand Greenwald. The man is a walking encyclopedia, very careful in his statements and touches issues of great complexity. One can rarely refute him in a one liner.