I could see right-wing videos getting hit harder than left-wing videos be a simple explanation, like maybe the right-wing videos got flagged more.
Maybe some gun control advocates were responding to pro-gun videos by flagging them as "promoting violence" or something stupid like that
And more flags = more moderators likely to see it, and thus more likely do take the video down.
That's an explanation that I could see satisfying even right-wing users as well - "whiny liberals reporting everything!!!"
The article says that PragerU filed a lawsuit against them for this, claiming First Amendment infrindgment.
It'll be interesting to see how that pans out, vs the whole "First Amendment applies to government censorship, not private property" thing.
Now, don't get me wrong here, I'm not supporting this type of "censorship", and even if the allegations are true, from a legal standpoint I would take the stance that I don't believe a private company should be forced to host content that they don't want on their property.
Come to think of it, isn't that typically more of a right-wing stance? I've seen similar arguments used by conservatives on other First Amendment issues,