He fully addresses that in the book. Don't take my word for it, I don't have his explaining skills.

But what he addresses is radical equality, as a fundamental value, as opposed to "less inequality". Equality under a ruler or rebellion against abuses is not the same as thinking the whole society as composed of equals. Think of no-slavery, equality among genders, sexual freedom, etc. Even thinkers that thought about equality before Iluminism (e.g. Thomas More) didn't go that far.

I strongly recommend you reading, at least, chapter 2 in the book. Is way deeper than what I explain.