This is because of the violence inherent in islam. The threats. Everybody knows this, but they choose to ignore this because they can isolate themselves from muslims. This will stop, for obvious reasons, and then we'll see what happens. But only one thing can happen.

I find it funny that people think that this is the first time this happens. In reality mass muslim immigration has happened many times in Western European history, and it has always started and ended the same way.

It starts with some abuse of muslims. Why ? Simple, because unscrupulous people bring in the first muslims, with the exact purpose of exploiting them as cheap labor (or worse, they're brought in as slaves. Given that muslim societies have slavery [1], this will often be an improvement of their situation). They don't care if they're muslims, just that they're weak and can be used. This goes on for a few decades. Does this have anything to do with racism ? No, it causes racism. If you look at it from the perspective of a normal worker in society, who sees his job being taken by masses of extremely low-paid and ill-treated muslims who do a shoddy job, but so much cheaper it's still worth it for the bosses, this will start to make sense.

This conflict with the poor, or lower class intensifies when the muslims' numbers grow. Because you can't compete with people who live like muslims do. So we get "tolerance". The reason for this tolerance is not some enlightened moral value, but because it is necessary to demand the same working conditions the non-exploited laborers get, to prevent society from degrading. To prevent a worker revolution (in the extreme case, which has never happened). So we get "tolerance". This is not a moral value, it is self-preservation of the poor, even if it can easily be mistaken for a moral value. Attacking tolerance as a social value is misguided. Fact is, as long as these minorities remain in society in significant numbers, racism must stop, or the lower classes must accept a huge pay cut.

Then the numbers start growing, and the threats and attacks start. Mostly you see the threats and attacks inside the muslim society itself, and sometimes at contact points (like intermarriages). Initially they are isolated groups, maybe individuals, attacking whatever they can attack because society rejects them. They are criminals at this point. The problem is that from a religious perspective they're right. They make the case in mosques that muslims should attack anything and everything around them, and their followers start to increase. They often get support from muslim institutions abroad. The attacks are necessary to attract attention, and to disable opposition and scare integrated muslims who do not share these ideas about their faith. Like always, the moderates will lose, they can't win through argument, and certainly they can't win the physical violence, when they're getting beaten up or killed (like islamic law demands they be).

This is the point we're at.

What's coming is a large scale "terrorist" act, not with a single perpetrator, but a large group of muslims (say 500-1000 or more) committing a large scale massacre in a large (probably) European city, after a while the local army moves in, because it gets no choice, and after the soldiers see the dead bodies "somehow" almost every muslim gets killed, including a couple hundred that weren't part of the "terrorist" act. (Ever wonder why there were zero female and/or children victims of the genocide at Srebrenica ?).

You have to understand the situation at this point. The population is not just mad at this point, it's furious. Both muslims and others. They are at eachother's throats. The government, however, is not weakened by these acts. The army is very nearly intact, and has zero hope of containing the situation. Also the army and the government are the only ones with an overview of the situation, so they at this point fully understand the situation : if they don't immediately act the slaughter will repeat in every city. So they do the only thing they possibly can ... Attack. They often don't take that decision immediately, they wait until it's made for them, resulting in a much bigger disaster.

Then the situation devolves into civil war. Here's the good news : muslims have almost never won such a civil war.

Needless to say, after this process minority rights are heavily curtailed.

This has happened dozens of times in European history, in various places, including places where you wouldn't expect it, like France, even Holland. It is simply happening again. Contrary to public opinion, history didn't die when the Berlin wall fell, it simply took a breather, because of oil, and frankly because America had both the chance, the military power and the will to make it happen for the last 3 decades or so [2], and history's resuming.

Muslims use scorched earth tactics. Their strategy is not to conquer, at least not directly. Their strategy is to destroy, and be the only ones left. In a primitive society where individual members are completely exposed to the most violent members of society, they will win. So they destroy everything until such a primitive society exists.

[1] in fact muslim societies are famous for how bad they treat slaves. Being a slave in the Roman Empire wasn't so bad (in fact everybody on hacker news who isn't a ceo, politician, soldier or -sometimes- consultant would have been a slave in the Roman Empire. Willingly. Read history to understand this). Islam is what gave slavery it's bad name (not that they were the only ones to treat slaves badly, but they were by far the worst)

[2] America, with the end of oil, is losing that power. Thanks to colonialism America managed to wield the power that oil gave middle eastern dictatorships (because their empire was militarily defeated and proceeded to collapse, to be taken over by Western powers in what is now known as "Colonialism". They have not rebuilt, and today there still is no viable candidate to resume where the Ottoman empire left off, plenty of contenders who want to, though). These days having America as an enemy is realistic for large states, and it will become positively easy when oil production really starts to drop (it started dropping in 2005, but so far only dropped something like 0.6% or so. This will accelerate a lot in the coming years even if shale oil has given America - but so far nobody else - a reprieve. It's nowhere near enough to bring America's power back to where it was 2 decades ago though. It is merely enough to keep America independant for a few years. This gives America the power to choose or refuse it's allies, a luxury almost no other large state has. For example China cannot choose it's allies or enemies)