It's not just the extremists, look what the Muslims as a whole are doing to France.
What are they doing? From what I understand the French are forcing integration by enforcing a very secularized public education system. It sounds somewhat discriminatory but it does appear to put everyone on even ground. I don't know enough about the issues to say more or understand the implications.
The Muslims have been rapidly immigrating, and The French have done exceptionally well dealing with it thus far (secularization laws). These laws are not discriminatory at all because the same policy applies to Christian and Jewish stuff as well. However, if they continue to immigrate at the current rate, they may overtake the country and reverse the secularization laws. Not to mention their birthrate is INSANE compared to native French, and they immigrate just as fast. Anyone who has been keeping track of this knows that they are seriously poised to overtake the country.
Well, there is that thing about democracy called the will of the majority. If the immigrating Muslims who become citizens wish to change the government to suit their needs, then that is well within their right. However, a state based around any particular faith usually has not stood up well in regions where there are multiple major religions, and the end result may very well be internal strife or ethnic tension.
You all can think what you wish; it could be a vast Arab conspiracy to bring down the West through turning popular sovereignty against democracies, or it could be just a large number of Arabs who see France and the West in general as being a better world than the Middle East and Africa. There are any number of options, though I personally believe that fear of Arab immigrants overturning the government is just as ridiculous as being afraid of the mass immigration from Europe to the US.
In many cases, immigration can do nothing but strengthen a country through allowing it to adopt ideas and customs of its new arrivals and their offspring. Hell, my weekly diet usually consists of fried rice from the Chinese takeout up the street and an occasional sitdown at the local Mexican restaurant just as much as I enjoy meals from places run by white Americans. Immigration usually can go over well so long as the country allows its minorities to integrate peacefully and willfully, not forceably as through France's secularization laws. If the Arabs and Muslims wish to remain separate and retain their culture while living in France, that is their choice; it is never the government's place to force a group to mix against its own will.