Have you ever been an immigrant? Ever seriously talked to one? They left their home country for a reason - as often as not, because they have an oppressive autocracy, theocracy or dictatorship. They tend to love their new country more than their old, and why not? You love France because you were born there by random chance. They love it because they looked at every country in the world, and decided France was the best one to emigrate to.
So immigrants tend to embrace their new culture. Most people who fled Soviet Bloc countries turned into ardent haters of communism - why wouldn't people who fled Muslim theocracies turn out to be pretty ardent haters of Muslim theocracies? They may keep the religion, but in a more moderate, modern form instead of the controlling throwback currently dominant in the Arab region.
And those are first-generation immigrants. What about their children? They'll raise them Muslim, of course, but they'll raise them *French*. They'll be well-educated and (knowing children) liberal. They'll hear the stories about how bad the home country was, and unless their new country does something to disillusion them (like your racist shitspouting) they'll be patriotic for *that* country, not some country they've never been to and hear only bad things about.
Since you call them the "Fifth Column", look at the supposed Japanese "Fifth Column". According to US Army reports from the time, most Japanese immigrants were Americans first, and the concentration camps not only went against the best intelligence, but was outright counterproductive, turning Japanese-Americans against America. And then look up the 442nd Infantry Regiment - Japanese-Americans fighting for America in WW2. With 3800 members, they earned nearly 9500 Purple Hearts (severely wounded or killed in action), 4000 Bronze Stars (acts of heroism or merit in combat) and 21 Medals of Honor (the absolute highest award in the US military). Oh, and they fought many of their battle in France - your country, in a small part, owes its current non-fascist existence to immigrants fighting against allies of their native land on behalf of a country that imprisoned their families for the very logic you support.
If you are an example of the other 90-95% of France, I think your country might be better off if you do let the Muslims take over. I know my fair share of people of that religion, and none of them are as reactionary and racist as you seem to be.