One could ask the identical question of American Blacks in the 1960s:
"If prejudice or pride in American society simply will not let you in, what are you doing in America?"
[Answer: 'I was born here, and have the identical right to be here and benefit from the society as the President of the Republic does.']
"Why not go where you can assimilate?"
[Answer: where would American blacks have gone to "assimilate"? Bigger answer: why should they have had to go anywhere?]
"Why stand around complaining until things get so bad that violence erupts, then blame it all on the opportunites he wasn't handed on a silver platter?"
Why, indeed, did those uppity blacks in America riot in the 1960s? Hmmmph. They should have accepted their lot and been happy with how good they had it.
"My gut feeling on this is it's a combination of no-win policies in their own lives combined with mob mentality/hooliganism."
Your gut feeling is partially correct. However, we can't know, because the government has made no effort at all to enable the hiring of these people, and to repress discrimination against them. How can you "assimilate" if you can't get a job?
"(Why is France still this way -- why hasn't the EU forced changes? I don't know, don't follow the minutiae of European culture.)"
The EU can't "force changes" like that. And besides, the rest of the EU's not any better. They're just not as tolerant of immigration period, and so have fewer immigrants than France does.
So you're saying they're justified in their behavior, plus insinuating that I'm racist.