> I fully agree that we don’t want to live in an aristocratic society in which already-wealthy families get richer simply by sitting on their laurels and collecting what Piketty calls “rentier income”—that is, the returns people earn when they let others use their money, land, or other property.
This is debatable. For one, aristocracy is not exactly this, as it is a system based on the notion of privilege, not just wealth. Concretely, it often means the same but still, using the word is quite misleading.
Secondly, one may argue that people, and thus families, should have the right to build stuff in the very long term, that is in a multi-generational way. Even if this thing they build is merely a framework of financial comfort. I doubt anyone would question the morality of offering gifts to children. So it's not clear to me why it would be wrong to give a child the means not to worry about money in life, and do it recursively through centuries.