They have to believe in meritocracy, that wealth isn't intrinsically tied to exploitation and a long history of classism.

Look at his history. He started out selling gum and candy to kids at school, then took increasingly demanding jobs (delivered newspapers and whatnot) until he went to college, after which he worked for his professor (IIRC, I don't recall specifics).

And he never was a day trader, so he's not the type that's making money on the margins off other traders, he's actually investing and sometimes buying a controlling stake in companies that he believes in. If you look at his lifestyle, he very much doesn't look like your typical billionaire, he lives in the same house he bought in his 20s, and generally lives a pretty modest life, especially given his wealth. Yeah, he makes a ton at his job, but he seems to be doing it because he loves his work, not because he loves money.

In my mind, he's basically the best possible example of a billionaire. He didn't do much of anything shady to get rich, he worked hard in his youth and invested wisely the rest of his life. And he started a pledge for other billionaires to donate the vast majority of their wealth, leading by example by giving away half of his wealth to drop from #1 to #2, and now to #10 or so.

If you're going to criticize billionaires, start with Gates, Bezos, Musk, Trump, or Zuckerberg, not Buffett. Buffett is about as ethical of a billionaire as you can get, and while there's room to criticize him, he should be nowhere near the top of the list.