de Sade WAS A NOBLEMAN; he is just the most infamous of that type of atheist at the time [look into Restif de la Breton, Gilles de Rais etc.].
The Enlightenment of the 18th century gave rise to atheism; Voltaire [among others - in case you try to say that he was an 'aberation'] was pouring scorn on Biblical truth in 1764;
"Some very learned dolts are quite astonished to find, when they read the VEDAS of the ancient Brahmans that they were unquestionably more ancient than the Jews; that the Jews should write in the Canaanite language only at a very late epoch, since they settled very late in the little land of Canaan. They say that the Indians were always inventors, and the Jews always imitators".
[Voltaire, 'Philosophical Dictionary' 1764]
Darwin was born in 1809, and his Origin of Species was published in 1859.

Among the ancient Greeks, Xenophanes regarded gods as anthropomorphic, as did Euhemerus.It is recorded that Renaissance genius Leonardo da Vinci was not a believer in God, and rather counted himself a "philosopher". Also, the romantic poet Shelly [prior to Darwin's 'Origin'] wrote a pamphlet called "THE NECESSITY OF ATHEISM" [1811], for which he was expelled from university [he followed this with 'A Refutation of Deism' in 1814]. This suggests that atheism was wide-spread amongst the elite since at least the Renaissance, but had to largely go about veiled in case of persecution. Shelly's revulsion was due to the stupidity and meanness of the Christian doctrine - he was not without spirituality.
Darwin's theory of evolution put paid to the Biblical 'truth' that the world began in 4,000 B.C.!

As for the implication that God has put some kind of 'copyright' on 'divinity', allow me a moment of golden laughter!
One can find the divine in the cosmos [as does Stephen Hawking] - we do not NEED to pretend that the divine is the sole prerogative of the God of the Jews! [No doubt the Jews would like to claim that they hold the lease on God, and therefore divinity!].
Fools.