I can't read French, but having evaluated many of these plagiarism cases in the past, a lot of them truly are witch hunts.

The plagiarism will be something like "Einstein presented a new theory: ___" and the ___ and several sections of the next few pages will be barely modified Einstein quotes.

Should they have used quotation marks? Technically, yes. But using them breaks up the flow for the reader, and it's not like they are failing to give credit to Einstein.

As an academic, I really would not care much if someone did this to my work so long as they mention and cite me generally.