No!! I don't believe that police don't target the Left. In fact, I have a strong memory of police violence against Occupy Wall-Street protestors.
My point, and my only point, is that alternatives to police are less accountable and less reformable. Even the FBI has to respond to freedom of information requests; and more than that, because the police and FBI are centralized institutions, they contain a chain of command at which specific criticisms can be aimed. Specific wrong-doers can be named. There is a public scandal surrounding unlawful activity by these institutions.
That's more than can be said about KKK vigilantes, who drive around with gun racks as self-anointed agents of God, who don't belong to a structured institution that keeps records, and, assuming that they even cared or bothered to investigate, can choose to completely ignore the actions of rogue members.
Government is certainly more accountable than private security corporations. Which group of investors will hold them accountable? Hint: it's not plucky Left-wing activists.
I'm out of my depth when it comes to dissecting these specific details. I don't have a perfect understanding of the capitol's security procedures. I don't know the exact role of the Proud Boys.Tarrio is the chairman of the Proud Boys and the FBI had at least 4 other informants in top leadership.
If you believe it was a spontaneous uprising you have to wonder why the police let the protesters in, why there was so little security, how the protesters unlocked doors locked with magnetic locks, and why the FBI has refused to answer any questions about its involvement with the event. The involvement of intelligence is the easier explanation; resistance to that comes only from the fact that that has a lot of implications about how politics operates in the developed world.
But I'll say this: Any "just so" story can be built around these facts in order to accuse literally any organization, not just the government, of conspiracy. An FBI conspiracy is certainly a possibility, but it is not the easiest explanation. The easiest explanation is that some pissed-off people were moved by inflammatory rhetoric.