This is not a net-neutral move by the Free.fr. Clearly some content is being treated differently than other content, based on source.
However, I think it’s up to users (and by extension, the services they purchase) to decide how to handle web content. Users might or might not like this particular move, who knows. But it’s up to them to keep using the ISP, or to change the setting in the router.
Under net neutrality law, should it exist, the ISP’s move would be illegal, no? Which means that Google uses regulation to ensure delivery of its product. Incumbency protection.
In fact, look for Google to posit exactly this net neutrality claim. My preference is that Free.fr and Google fight for your affections.