Richard Black, who appeared on controversial Jubilee video, organized Proud Boys-linked protests in 2017

A debating opponent of the leftwing media figure Mehdi Hasan in a controversial viral YouTube video was previously the organizer of two violent far-right protests in Berkeley, California in 2017, the Guardian can reveal.

The video debate session with Hasan, published to the 10 million-subscriber Jubilee channel, has already attracted scrutiny due to platforming a self-described “fascist”, Connor Estelle, who reportedly lost his job after he was identified by online researchers.

Unidentified until now was another of Hasan’s opponents in the debate video, Richard Black. In conversation with Hasan, Black refused to condemn violence against police officers, claimed that the Los Angeles police department was directed by “liberal Marxists”, and described his own political position as being “white nativist”, adding that “neocons, libertarians, all those mainstream people, [they] might as well be leftists to me”.

In March and April 2017, meanwhile, Black organized counter-protests – later referred to as the first and second “battles of Berkeley” by the US far right – that pitted members of the Proud Boys and the Rise Above Movement against protesters who opposed a campus speech by the far-right provocateur Milo Yiannopoulos.