So I'd argue that the French have a love-affair with traditional publishing, and traditional publishing loves draconian copyright rules.
The whole thing is almost a culture war for the French people's soul by-proxy.
This sentence is ridiculous and has nothing to do with scihub and libgen. Most french researchers are perfectly happy using these sites, and dislike strongly the draconian schemes of scientific journal publishers (which publish texts mostly in english). Several people are pushing for french university libraries to stop paying subscriptions to journals and give all that money directly to scihub. Yet, these initiatives are always blocked at higher levels.
I think this has more to do with the copyright lobby than anything else.
[1] https://www.lemonde.fr/sciences/visuel/2016/05/10/edition-sc... (in french)
[2] https://www.the-scientist.com/daily-news/french-universities...
But everything to do with the French government's attitude towards traditional publishers and why they work so closely together. This issue doesn't begin and end with research publishing, it is bigger and older than that.
Calling something "ridiculous" simply because you want a black & white answer to a larger complex cultural phenomenon is a little disappointing.
Well, someone has to.
In this case I have no pity for them, then. If they want to feel better about themselves by cutting off their own ears because other people are using English then let them.
Now please don't consider this ruling as one made by the actual researchers, especially the younger ones that had a decent English education and sees no problem using English material.