A behaviorist friend used to assure me that all human behavior can be explained in behaviorist terms. I used to test him, and sometimes I felt I had won the argument, but he really did demonstrate to me that his framing of the world could go a long, long way toward explaining things. Even more than punishment discouraging a behavior, rewarding a behavior encouraged its continuation. I find it is rewarding to look at the rewards, punishments, and lack of rewards in any ongoing situation to see if it explains something I missed.
People who assert that America is a racist society do not usually do that in an individual conversation. The emotional rules are different when you have to look someone in the face. (That is true of conservative fire-breathers as well.) For openers, people try to take the subject down from talking about all of America, which neither of you can do much about, to more local, or even individual issues. Not always. Some people need to make intense declarative statements in all circumstances.
But if you make a blanket statement in a book, or on a news program, or in an editorial, or on Facebook, or as a spokesperson for a group, what happens next? No matter how many people try to answer you reasonable (whether politely or rudely), you can't count on someone who actually is racist making a comment. And that rewards you for your assertion. It proves you right. Any discussion of whether that person represents 10% or 0.1% of the population does not matter in terms of the reward you get. Those of us who read comment sections see this all the time, even on fairly reasonable sites. You read people making more or less reasonable replies. Then you hit that same knucklehead who never seems to go away,and he - it is usually a he - makes some pants-soiling racist statement, and the rest of us shake our heads. Just shut up, will you?
He's not going to shut up, for similar reasons. When he makes a stupid statement, someone will get infuriated and make an accusation back at him that is at least partly unfair. See, I told you. These people always claiming racism are just evil children themselves. That's pretty rewarding to type on a site where you know lots of people will see it.
When Don Lemon, selling a book, accuses the whole society of racism, any number of folks would like to get him into any sort of moderated debate about this, or any situation where he had to take actual questions and be hounded until he answered them cleanly.* But that is never going to happ0en, and he will never feel the need to make a logical argument, because in his mind, eliciting the racist statements he was trolling for proves his point. That they don't prove his point does not matter in behaviorist terms. His behavior was rewarded, he will repeat it. So will the people who agree with him, waiting for the inevitable actual racist to make an appearance. The only negative consequence that would have effect is complete deplatforming, as they would no longer have any way to get those chemical hits. We know that is not going to happen.
We keep hoping that some persuasive argument will break through, or if we are angrier, that some crushing response will shut him, and them, up. Have they no shame? Can they not see the hypocrisy and inconsistency? Irrelevant questions. They are pigeons hitting the bar for another pellet.
*That is all I ever wanted with Bill Clinton as well, to be made to stand in the well of Senate and answer questions.