White Fragility: Why It's So Hard for White People to Talk About Racism
The same author gave a great talk about the book: smart, funny, and very informative: https://www.youtube.com/watch?v=45ey4jgoxeU
I do agree that people are racially distinct, but only if people are trained from an early age to treat those specific racial as significant. In Africa there are 27 major ethnic groups; to Africans those are visually distinct. To Americans, they're all just "black". The category of "white" is similarly artificial.  The boundaries of "white" have varied greatly over the years. So yes, I agree Americans will quickly classify somebody by race, but it's not primarily a visual difference, but one of specific cultural training.
I am saying that "special" treatment is not at issue here. The treatment was not just special; it was somewhere between suspicious and hostile. One of my colleagues there was just short of 7 feet tall. He was visually distinct but read as white. He often got treated differently, but never suspiciously. I doubt a white dude in a wheelchair would have gotten the third degree; my expectation is that people would immediately open the door for him.
As to calculus in high school, I know plenty of people who are programmers without it. I certainly have never used calculus while coding, so it doesn't make a practical difference.
As to how you can help, I think the best things to do are a) learn about America's history here, b) learn what present-day social structures help continue the diminished-but-still-ongoing oppression, and c) talking about them frankly. As somebody who didn't grow up here, you'll be able to see and talk about these things in a way that white people will listen to. Good books include Loewen's "Sundown Towns", Ijeoma Iluo's latest book, and Julie Lythcott-Haims recent memoir.
I hope that helps!
Second, I never said he was racist -- that's your interpretation. I specifically avoided that term because when white people are experiencing white fragility , which is certain to happen in a large group discussion like this, then they immediately cast any incident in into the common post-Civil-Rights-era frame of "racist=bad person" and start defending their fellow white person, who surely must be good. What I talked about was unconscious racial bias.
Third, your demanding "proof" is unreasonable. What would count? Should I have fMRI scans done of the person's brain under various stimuli? Even that wouldn't be enough; you could argue he might harbor racial bias, but that it wasn't active at the time he grilled my intern. I just looked at the last few pages of your comments here, and you have offered all sorts of reasonable opinions without ever giving a bit of proof. You are bringing up a standard that couldn't possibly apply and that you don't hew to yourself. You might ask yourself why.
Fourth, I included evidence. First, there was the testimony of the one witness who, even though he's still in college, has had to become an expert in America's still pervasive and demonstrable white bias against black people. Second, there was my testimony as to the nature of the environment and the rareness of an event like this. Third, as I mentioned, I talked about this with my boss. In all of our judgments, under the preponderance of the evidence, this was an unconscious racial bias incident. Nobody at the company thought otherwise, including HR and the black employee group, who deal with this sort of thing regularly at that company.
Fifth, it's not my job to prove anything to internet randos. It's your job to understand America's racial dynamics and how this fits in before commenting. I told this story knowing full well that I'd get salty replies from people who would react with instant denial to any description of a bias incident caused by someone like them (a well-meaning white tech dude). Why would they do that? Well, if you have studied American racial dynamics, you'll already know the answer to that. And if you haven't, I recommend that you read one or two of the four books I've already recommended in this discussion. You'll learn something.