A more fundamental mindset is, in my opinion, at play.
Leftists, expecially white, dedicated Leftists, feel that because they are often “down with the cause”, it makes them immune to violence from the people whose causes they choose to support.
In this case, it is a case of a dedicated, ideolocally-bound Leftist who assumed that everyone he might meet would immediately understand he was on their side, fighting for their cause, whatever that Leftist cause might be.
It emboldens them to be in areas that they shouldn’t be, at times they shouldn’t be, and they think because of their hair, tattoos, slogans on t-shirts or hats, whatever, that anyone from the side they profess to support would immediately recognize their fealty, and not harm them.
Solzhenitsyn recognized well this dynamic in his observations of Soviets who were all in on the Communist Party. They wholeheartedly believed in it. They supported it.
And even when they didn’t believe it fully or whole-heartedly support it, they thought that pretending they did would shield them from the consequences of what they prefessed to believe in.
But when that heavy knock came on their door at 2 AM, which they answered with blinking, sleepy eyes to be told they were under arrest, they were astonished and puzzled, saying “Me? Arrested? What for?” and they really expected there to be a valid justification. They didn’t realize the Communist cause they supported and bought into was a thoughtless, blind predator, beholden only to the whims of some official who didn’t care a whit that they stood up and applauded Comrade Stalin for his tryannical efforts.
They would be dragged away, screaming, saying “Why? Why? I am on your side! I am one of you!”
In the same way, this guy who was stabbed, not by a tyrannical bureaucat taking orders from a list given to him, but by a person who was taking his murderous marching orders from a steambath of racism he was enveloped in, must have lain there on the ground, unable to speak, thinking “Why? Why? I am on your side! I am one of you!”.
And no doubt, the woman with him likely was screaming aloud in puzzlement and frustration “Why? Why? We are on your side! We are down with your struggle!”
In these cases, I recall the quote uttered by Clint Eastwood’s character (William Munny) in the movie “Unforgiven” when he heard the dying Sheriff mutter, just before Munny blew his head off “I don’t deserve this.” to which he answered “Deserves got nothin to do with it.”
This guy who got stabbed didn’t deserve to die, even for supporting racism as a BLM supporter or associating with people who fully support racist killings as long as it is them doing the killing. But he didn’t know that racism is a double-edged sword that cuts in both ways even if you support or don’t support it. He was on the cutting edge of that sword that swung in his direction.

“This guy who got stabbed didn’t deserve to die”
Very articulate post, however he played a stupid game and won a stupid prize.
Once I had to go up to Washington DC to bid a contract, I kid you not, a job site at the corner of MLK and Malcolm X. Talk about a bad intersection.
It was at a school, and the black principal of the school told me in advance: "Park directly in front of the school by the front door. Come in immediately. Do not walk around the neighborhood".
“I don’t deserve this.” to which he answered “Deserves got nothin to do with it.”
~~~
One of my all time favorite lines in movies.
Even though there is a dark twisted way to find william muny a sympathetic character because he is getting revenge for the torturous death of his life-long friend, he is basically a (alcohol induced?) psychopath who spent the last 10 years of his life convincing himself that he wasn’t one, but it wasn’t until he imbibed again that the monster came back out, and he explained in one line how the human evils of this earth work. Fairplay, ethics, morality, and empathy, they don’t register on the motivational scale of a psychopath.
People, because they spend their entire life circulating around moral people as well as the immoral people who aren’t evil psychopaths but live in a truce with ordered society, they think they are somehow protected from evil. Sometimes you are unfortunate and evil finds you, but more often then that, particularly with people like this, they are putting themselves in the presence of evil. They are taking risks and they are willfully blind to it because of their naive idealism