He could write essays and put them on the internet for people to disagree with, I guess. Trying to convince people of something that they're dead set against is exhausting. He describes spending 2.5hrs one night educating her. That was just that one night, and he implies many many more hours personally educating her. How many people should he have to personalize an education on racism for before he's done enough?
Clearly, his method of "education" isn't working, or his target audience is the wrong one. I never asked for a personalized education. If he was trying to lobby Congress or make a YouTube video or hell, run around the sidewalk and hand out pamphlets, I could see his viewpoint and point to a concrete solution that he's trying. The problem seems to be that he doesn't actually want to find a solution, evidenced by his lack of communication with white people. How can you claim to want peace when you don't even want to talk to your enemy?
His entire point is that the method of educating isn't working. It's not working because the audience is often actively opposed to being educated. They like thinking that racism is a non-issue and they enjoy that their willful inability to learn can be misrepresented as him unable to "prove" to them otherwise. They enjoy this as a license for them to continue the status quo. In asking them "what would it take" he would be given insight in to exactly how badly they refuse to learn. Their answer to his question is a lede and then the goalposts never stop moving. He'll never convince them because they are subconsciously resisting fact and reason. They like the world with the wind at their back. If the question was "what would it cost to convince you" their answer would essentially be "you don't have enough".