I agree with your final sentence about systemic racism: "In other words, it isn’t really about you. But how you respond to it, most assuredly is."

"If you're not part of the solution, you're part of the problem," as we used to say. Even if a hiring committee doesn't state in advance "We're not going to hire any black people for this position," they can't be unaware that everyone who held the position previously was white. If they don't care enough about the inequity to help fix the problem, then they are locating the source in some sort of deficiency based on the race of the people they pass over. They are supporting systemic racism, and they deserve to be called racists.

But I disagree with your previous point that the intent of someone committing or abetting a racist action is unimportant. I don't think there are any accidental or unintentional racists.

"But regardless of whether you don blackface out of ignorance or malice...."

How can someone don blackface out of ignorance? They thought it was sunscreen? People are discriminated against because of their skin color. When Jimmy Kimmel (or anyone else) put on blackface, he was exploiting someone's vulnerability for the sake of humor (and profit). His action was intentional and it was malicious. The fact that other people before him had donned blackface doesn't excuse him--it makes what he did even worse.

"To deny the pain of the injured by focusing on the intent of the injurer is to suggest that the injured is not suffering, or if they are, it is only because they are irrational — yet another insult heaped upon the original harm."

Again, I think the mindset of the racist is always significant, which is not to say that the damage a racist does is insignificant. If no black people had seen the Jimmy Kimmel blackface episodes, would Kimmel be innocent of racism?