> At the basic level, a farmer who sows a field and harvests a crop is making the world one harvest richer, and no one poorer.
Not quite true; the farmer using that land to grow crops is externalizing an opportunity cost onto those who might use that land for something else, e.g. for the carpenter's workshop or the mechanic's garage. Same with the water consumed by those crops. With these natural and finite resources, there very much is a zero-sum game, since your use of that resource is at everyone else's expense.
This is something Graham entirely misses in his article: the wealth, contrary to his core assertion, does flow from a common source, specifically land. The wealthy, in turn, are such specifically because they happened to be the ones able to control that land at the exclusion of everyone else. This was the basis of Henry George's advocacy for a land value tax.
"But YellowApple," I can already hear, "${ARBITRARY_FAANG}'s wealth ain't tied up in real estate!" Au contraire. Their software is developed in offices that consume land. Their hardware is built in factories that consume land. Their hardware is further constructed from materials extracted from that land. It's land all the way down, and the company externalizes those opportunity costs on everyone else. That is where the injustice in their wealth lies; it is unjust for them to reap the benefits of that land without adequately compensating the rest of society for the opportunity cost the members thereof now bear.