Honestly, if anyone else had told me this story, I'd assume that they were either exaggerating or that they were being an asshole to the other person in a way that made them shut down and not really want to engage with them, but it's as near to an accurate recollection as I can make it. I've taught programming to people from all walks of life, from 13 to 60+ years old, I've mentored quite a lot of devs, I've taken kids from "yeah I'm interested in computers, I like playing games" to senior developers, and while I'm sure that my teaching style may not be perfect for everyone, I've never once heard any complaints that I made someone feel stupid, belittled or like they couldn't make mistakes. I always encourage people to be as honest and open about what they do/don't understand because if someone says "I don't get it" I can explain something in another way that might make it click. But yeah, that day when I had just been through the whole for-loop thing and he asked me about integers again, it was as close to just completely exasperated as I've ever been with mentoring someone. It was a surreal, groundhog day feeling, like I was sisyphus, and my boulder was explaining to a computer science graduate what a whole number was.