I've taken the liberty to chop up your post and reorganized it into two chunks to address separately. I hope this is acceptable.
I'm not ignoring your comments; just digesting them. The Proud Boys scenario I thought involved shoving people to the ground, not clubbing them with a baseball bat. I'm still mulling over whether I believe (all?) cops are institutionally aligned with right-wing violence.
Interesting developments in the Reinoehl shooting, waiting to see what else comes out. The initial Justice Department statement seemed carefully tailored to accommodate a wide variety of scenarios, from summary execution to absolutely justified return fire on the part of officers. I have no trouble believing Reinoehl was armed; I would be surprised if he wasn't.
I wish Reinoehl had stopped with shooting the can of bear spray (and Danielson's hand in the process). But, no plan survives first contact with the enemy. Don't worry, I'm not swayed by the "crocodile tears" of the right. I just see how others might be - without being literally Nazi collaborators.
Based on experience with firearms, I think it's extremely unlikely that Reinoehl intentionally struck the can of bear spray. Jokes on my part about marksmanship aside, it's almost inconceivable that someone shooting at a person would even attempt what is essentially a trick shot or be successful. In all likelihood, the can was just hit incidentally as Reinoehl fired at Danielson. I don't think there was enough time between the two shots to assess the situation.
I think there's enough evidence that Reinoehl may have had a legitimate self-defense claim. The video clearly shows Danielson firing the mace first, and his collapsible metal baton was seen open on the ground near his dead body. Given that Danielson was part of a mob of people that spent the day pepperspraying and clubbing protesters on their convoy through the city, it does't strike me as that implausible that Danielson may have been the aggressor here. Given that Reinoehl was killed by the police, there will be no trial and likely no deep examination of the event to find out the truth, so there's not much point in splitting hairs about it now.
Self-defense or not, your second point I find the more interesting question.
Maybe I'm a bit thick but you make a key point that I really hadn't put together before: IF cops are institutionally aligned with right-wing violence THEN left-wing vigilantes are justified in using even pre-emptive violence against alt-right counter-protesters. Not only justified, but commendation-worthy. "Good, another fascist dead" seems to be a fairly common response.
I'm not sure you're wrong, but what then is the correct moral action?
Police aligning themselves with the right and granting them a free pass to commit political violence is a very serious problem, and it doesn't really leave a lot of good solutions.
The best possible one would be for pressure to be placed on the cops to stop this corruption. The first step in doing so is publicly and forcefully making the accusation, and for people in power to acknowledge that it's a problem. It's a form of corruption, the police are using their authority in order to advocate their own political interests. How exactly this kind of corruption can be addressed, I'm not sure. I would note that, while related, this is not the same issue of the police brutalizing protesters during anti-cop protests. It's entirely possible for PPB to continue gassing and beating anti-police protesters and to crack down on right wing violence.
It wouldn't take many non-corrupt cops, granted the appropriate authority, to start making arrests of the known violent actors in the PNW scene. There is a core of known violent agitators that are spearheading this fascistic violence in the streets, and there exists right now enough evidence to place most of them under arrest. Alan Swinney is a useful "canary in the coalmine". His continuing immunity from police action is a clear signal that the right has permission to continue to commit violence.
If the police corruption is not or cannot be addressed, there's not a lot of pretty options left. If permission is granted to the right to commit political violence, the moral action is to violently oppose it. Legality largely goes out the window as cops are intentionally creating an atmosphere of permitted lawlessness for their allies. Antifascists should try to avoid legal entanglements and consequences for self-preservation reasons, but this is by no means a moral imperative to remain non-violent in the face of fascist violence that is allowed by the police.
Danielson wasn't just some random MAGA hat guy that got targeted by a antifa type and murdered. He was part of a Patriot Prayer mob that is organized around the goal of committing violence against the people of Portland. He was wearing the uniform of an organization that spent the day attacking the city, and was armed. In short, he was a member of an informal street army and died a soldier's death. I see no scandal here, other than the obvious scandal that the police are endorsing this sectarian atmosphere.
When it comes to uniformed neo-brownshirts such as Proud Boys or Patriot Prayer, I think wartime rules of engagement become morally acceptable. These people are modern day fascist Freikorps. So long as they remain open belligerents, they are fair game by hook or crook. Mutual firefights, ambushes, assassinations, whatever. This isn't a boxing match, it's straight up combat. There is no moral imperative for "gentlemanly war" or waiting for the enemy to fire the first shot.
There are two groups right now that can de-escalate this situation and restore a moral peace. The fascists can stop committing attacks on non-violent political demonstration, or the police can start arresting them when they commit violence. I don't see any way for the antifascists to restore peace other than to cede the public sphere to fascists and surrender their rights to political expression, which is unacceptable for the obvious reasons.