The company wasn't specific about which channels fell afoul of the unintentional move, although the Outline (which broke the story) detailed a wide range of affected accounts. Some of them, such as Anti-School and Destroy the Illusion, explicitly peddle in conspiracy theories. Others, however, don't appear to have obvious violations -- the Military Arms Channel saw three gun videos taken down. Some of MAC's videos had been restored as of the afternoon on February 28th, but none of the affected channels were back.
Some outspoken conservatives, including some of those affected by the crackdown, have accused Google of trying to censor right-wing politics through moves like this, including an earlier action against Infowars. They leveled similar accusations against Twitter when it removed thousands of their followers, although that was debunked when it turned out that the social network was purging bots.
The incident highlights the problem YouTube faces when policing it content. It knows that algorithms alone aren't enough to detect offenders, but also has to contend with human nature -- it can't guarantee that people will flawlessly interpret the rules, especially if they're inexperienced. That's problematic by itself, but it's worse when it happens in a politically charged atmosphere where people will accuse it of systemic bias.