>Her basic assertion was that the simple accumulation of that much wealth is itself evil. They could do many things like build schools and since they choose not to they are evil.

This is, essentially, a debased version of the standard leftist argument that economic systems that permit this sort of concentration of resources are fundamentally broken.

Since people have to personalize everything into morality plays, the idea that the existence of such people is symptomatic of something broken in society turns into these people are why society is broken.

Granted, since they DO have the resources to fix a lot of issues and choose not to still doesn't say anything good about them. There is something to the adage that if you're not part of the solution you're part of the problem. And if you're directly profiting off the problems, potentially spending money on lobbyists and political donations that prolong the problems, and bidding for contracts with groups that are directly responsible for the problems. . . it starts to get a bit dicey.

The way the economy is, it is extremely doubtful that anyone can accrue that kind of wealth without having their fingers in at least a few morally questionable pies. Like, if you were a steel magnate in Nazi Germany, you were definitely involved in making the holocaust happen regardless of your personal feelings on the matter. If you didn't, someone else would have though, so how much are you really obligated to address?

Andrew Carnegie, the 20th century industrialist, is perhaps the poster child for wealth accumulation and subsequent philanthropy. I remember reading somewhere that he once said something to the effect of, "A man should spend the first third of his life learning as much as he can; the second third amassing as much money as he can using his acquired knowledge; and the last third giving away both the knowledge and the money."

The profit comes from the labour of people who work for you. Any profit you make is the difference between what their true labour is worth and what you pay them. So unless the owners are adding billions in value by themselves they are paying people less than the true value of their work.

The extent at which this happens is where some ethical issues lie. If you keep wages low while making large profit there is a point of view that you are ripping off your workers and this can be seen as unethical.

Cooperatives are designed to address this by making all workers joint owners. https://en.m.wikipedia.org/wiki/Cooperative

There is also the argument that large corporations that legally avoid paying tax and lobby to keep the loopholes open are making money by utilising public resources and not paying for them. These public resources support their workers and help the company to succeed. Bezos for example is particularly successful at avoiding tax and lobbying to keep it that way. Despite it being legal it could be considered ethically dubious as he is not contributing back to a system that helped him succeed.

Depends on how you define worst of the worst.

There aren't that many billionaires. So are you saying they aren't the worst of the billionaire class? That's really the only way I can see the phrase working.

> I mentioned to her that they can’t sell their stock without ceding control

What about changing voting schemes?

> Does it say something about someone’s heart if they aren’t building schools and hospitals the moment they obtain enough wealth to do so comfortably?

I think it says something about their heart if they are able to get that wealthy, with rare exceptions.