They aren't French. They are not culturally French. They are not ethnically French. They live in France, but are not related to the native population (unless they've interbred), and they do not share a culture with the native population. They remain both ethnically and culturally Turkish or whatever nation they've emigrated from.

The idea that because you are born in a certain region, that makes you a full member of the cultural and ethnic group native to the region is flawed. Countries of immigrants, like the US and others, use this to define membership, but old world countries have historically been defined differently. They are cultural/ethnic/lingusitic nations, not just geographic, and therefore the idea of "If you're born here, that makes you fully French/German/Norwegian/Spanish, whatever doesn't work out as well as the same concept in the US. Thus, problems can arise. I think too many Americans are trying to apply our concept of nationality to nations that have a rather different background.