Put another way, only in the US do businesspeople have to publically apologise for not-being-nice. Towards the end of the video, Kalanick was brusque and even demeaning, but I don't think his position as CEO grants me the right to get high-and-mighty on my keyboard and demand he "grow up." Nor do I expect much insight into anyone's character can be gleaned from a 30-second argument in the backseat of an Uber.
I'm not saying Kalanick is a good (or a bad) CEO. But his job is to build the company, not to serve as its' Mascot-in-Chief.
This was not a mere failure of niceness, as if he didn't say please and thank you.
He was also unkind, arrogant, self-centered, thoughtless, ungrateful, and foolish. As well as failing to demonstrate compassion and moral responsibility.
You're also wrong on what CEOs are supposed to do. Companies are made out of people. His primary job is as a leader of people. The way you build a company is mostly through getting a hundred thousand small interactions with people right. He visibly failed as this guy's boss, just as he's been privately failing to build a sane company culture.
An important secondary job is being the public face of the company, the human representation of the brand. Even if you are a terrible human being, it's your job to get up there and simulate being the kind of person that people would like to associate with your brand.
I'm not saying Kalanick is a good (or a bad) CEO. But his job is to build the company, not to serve as its' Mascot-in-Chief.