At the heart of this article is the claim that buying equity is a form of theft. That is an extreme claim (in the sense of surprising, remarkable, unusual, and one that needs a lot more support than ordinary claims). It is inadequately defended here. The argument that it violates fair exchange is tautological.
So yeah, even though on first skim I think I agree with the thrust of this article, I think you're right it's poorly defended, assuming it's at all for an audience outside of people who already think this way.