It's not beyond the realm of possibility; I recall a convert to Islam (that looked rather out of place with his red hair, etc.) in the UK trying to perform "sharia patrols" in the streets.

I contest believing that young people going to beach in France or Italy would give even passing thought to what these people think or want, because it's completly outside the realm of my experience of the people that I've ever known to go to the beach, ever. A vastly more likely consideration is avoiding unwanted attention from people that approve of mostly undressed girls.

I don't think that you understand (I don't know, maybe you live here?) how socially -isolated- immigrants are.