Exactly. Holland’s temper is suspicious. He seems overly sensitive, like he has an axe to grind (because he grew up as a Christian, like Bart Ehrman), and like he knows unconsciously he’s pushing the line of argument too far.
Of course, Christendom had an impact on modernity and on secular humanism. It’s like how a native language will shape how you speak a foreign language, by setting your accent. The language modernity speaks was closer to Greco-Roman naturalism than to Judeo-Christian supernaturalism, but the early modernists’ accents were Christian. They expressed ancient concepts using lingo derived from the Bible and the Church, such as the figure of speech of a “law of nature.”
This is a tempest in a teapot for me, though, because Judaism and Christianity were themselves influenced by the Hellenistic period, so there’s no firewall there for Christian apologists who want to give Christianity all the credit.
Regarding “Jesus was Socrates for the masses,” I think that claim is somewhat vacuous. What they mostly had in common was their counterculture which got them both executed, but Socrates was a humanistic philosopher, not an apocalyptic preacher. The question is which Jesus is at stake. The gospels’ portrayals aren’t consistent or coherent.
Did you rewrite your comment here? I thought you said earlier that monotheism supplied the unity that modern secularists presuppose. Yet the ancient Greeks already had the concept of a cosmos, of an ordered whole universe. The Presocratics reductively explained everything by positing a metaphysical substance such as water or fire. That unified perspective goes back to the Axial Age, I think, so monotheism is only one expression of it.
As to why modernity happened in Europe, it could be that Christianity played a negative role, spurring advances by its repressions of philosophy and science. This would be the forbidden fruit syndrome: a child rebels against his repressive parents, so the repression negatively motivates creative ways of sabotaging the police state. Or it’s like how the Japanese had to get creative with their pornography to get around the censors; hence, tentacle porn, etc.
