I think the most salient part of this is the remarking that being a billionaire is immoral.
I don't think being a billionaire is necessarily immoral, but I definitely think it's incredibly difficult to do so without being immoral. I think the closest examples I can think of are people who weren't even trying to become wealthy - I doubt anyone whose goal was to make fat stacks of cash would, for instance, start writing young adult fiction on napkins in a pub in Britain, or start writing a voxel-based crafting game in Java. And unfortunately even these two individuals aren't remotely close to paragons of virtue.
That said, I think the biggest sin of Jeff Bezos' is just being complicit in the whole system that keeps our tax code a disaster. I would feel a lot better about the wealthy, and mega corporations, if I felt like they were appropriately paying for the community resources they use, for example:
* public universities and education that educate (and train, to some degree) their workforce
* public services that cultivate the kind of safe and secure society that allows people to focus on things that aren't subsistence or physical security
* infrastructure that makes their existence possible - roads their employees drive on, DMVs that their employees register their vehicles at, water systems their employees drink at both work and home, power systems that provide stable electricity, etc etc etc
* And it's not just your employees, it's your customers too. If we didn't have all of the above, people would have a lot less psychological, financial, and physical safety to need anything Amazon sells.
* And something that I think really goes under-noticed: the world's best-regulated, safest, most reliable, most well-understood, and most liquid securities market. Both private and public. So much goes into making all of that crap (I say this semi-affectionately as someone who used to work in the sector) work, and it's where an enormous percentage of both these companies weath both lives and came from.
I think you see where I'm going with this. All of the wealth that's generated here is entirely predicated on, and a product of, this incredible foundation we've built collectively as a society. And the bigger you are, the more wealth you generate, the more of this system you've taken advantage of in one way or another (with some of the secret sauce of these companies being that their employees and company take a relatively small amount of it, while their reach scales to so many more customers, that they disproportionately (compared to other companies) take advantage of huge swathes of the customer side of "benefiting from the social foundation".
This is the main thing that irks me. They would be nothing without all of this, and yet they can use their wealth to skirt out of paying their fair share, even though it really seems to me that paying their fair share - paying back into the system they benefitted from - is probably better for them in the long run (50+ years) as they'll have more educated employees, more stable customers, and so on. It's a giant feedback loop that they're short-sightedly intentionally not paying back into.