But contrarely to what people think, crime isn't IMHO the worst of them. The worst is the feeling that the cultural norm of the country, as well as its "visual" identity has shifted from a european country to a (mostly) african one ( and please read the rest before making hasty judgments on what i'm saying).
To understand the problem, imagine going to a few remote rural areas in japan in 40 years and each time only see tall 7 feet blond and blue eyes people, speaking swedish and not finding sushis or ramen anywhere.
I like all cultures, and i believe there's great things everywhere, but that's why i'm also a bit sad to see "traditional" France (whatever that means) disappear.