You are talking about an event in the Great Terror (https://en.wikipedia.org/wiki/Reign_of_Terror), when thousands of people were executed by the Committee for Public Safety, both on the left and the right, as Robespierre descended into madness. Towards the end, he set up a festival in which he invented his own cult -- the cult of the Supreme Being, and posed as moses carrying the revelation of the Supreme Being from a mountain. That really started to freak people out.

Pronouncements from that era are not representative of French culture or thinking even a few months after the terror. For example, Napoleon was a great patron of science.

BTW, a fantastic source on the French Revolution is the revolutions podcast -- they cover it over 53 episodes

http://www.revolutionspodcast.com/

One of the more poignant episodes towards the end of the Great Terror was when, in one day, they executed a group of nuns whose only crime was living together communally, and a 16 year old pickpocket. Whereas before, the citizens were cheering on the Guillotine, towards the end, when the boy was beheaded, someone from the crowd shouted out "Please, no more children!"