selection bias

He's not doing a formal study that requires random sampling. This is his blog - opinions & thoughts.

He makes the claim that nothing is done about right-wing protesters

I've read the article and I don't see him making this claim anywhere. The closest I can see to it is one of his opening sentences where he writes "actual terrorists (especially on the far right, and especially in the US) often remain unmolested by the law".

One of his topics here is the disproportionate punishments handed out to left-wing protesters (esp. peaceful ones). He talks about what he calls "extrajudicial punishments" that don't even require convictions to cause massive harm to the protester. The UK gov't seems to be pioneering these techniques to dissuade and crush public left-wing protest, but if the techniques are successful it's just a matter of time before they're employed here in the US too.

Ragebait? I guess, but given that the topics are legitimately rage-inducing, that's to be expected. While right-wing domestic terrorists in the US continue to ramp-up their threats, and acts, of violence against those they dislike (including insufficiently MAGA-loving elected officials and judges ), with very few of them being caught and punished (never mind having their terrorist networks broken-up), following the UK recipe, we have (source):

Protests against the proposed training center — dubbed “Cop City” by opponents — have been going on for more than two years. Georgia Attorney General Chris Carr obtained a sweeping indictment in August, using the state’s anti-racketeering law to target the protesters and characterizing them as ”militant anarchists.”

Demonstrators and civil rights organizations, including the American Civil Liberties Union, have condemned the indictment and accused Carr, a Republican, of levying heavy-handed charges to try to silence a movement that has galvanized environmentalists and anti-police protesters across the country.