Siro, I am immigrant myself and I chose to accept everything my new country has to offer - even if it is way different than my country's tradition, laws, etc. We celebrate our national holidays or keep our traditions within the family and close community but we do not REQUEST or DEMAND it to be accepted by the rest of the country. There would be no problems with multiculturalism if everyone leaving their old countries would have same mentality and leave their old habbits and rituals there as well or keep it at family, community levels only. Just put your new country above your own personal needs! Accept it and become real part of it!
I am bringing my soccer team as example again - we are tied group of friends and we have people form all over the world, I counted 9 countries and actually canadians are minority but we have absolute fun and blast together and nationalities or religion was never an issue. Yeah occasionally, somebody in the party will not eat pork or drink, but that does not bother or offends anyone.
Why everybody can't be a big happy family at the country level? That is a million dollar question right there my friend and I would love to know the answer.
Just because you don't like certain cultural mentalities does not mean that multiculturalism is a bad thing. Would you be opposed to Westerners pushing their cultural norms like free speech and democracy on others? Well, they do. And it works. The world is becoming more open and more democratic because the Western approach is the best model for development. You're opposed to Muslims trying to impose their cultural norms because you think those norms are backward. You're worried that the open market of ideas won't prove an adequate check because Muslims multiply a lot faster than most other groups. Your concerns are understandable.
But without multiculturalism, we're all doomed. Unlike many people, I am of the opinion that humankind has been on a trajectory of progress in every meaningful sense for thousands of years. The main reason for that is the proliferation of information into larger and larger groups. The Greeks had many brilliant ideas and insights (easily the greatest classical civ). When Middle Age Christians rediscovered the Greek legacy, it had been substantially and profoundly expanded upon by Muslim scholars. The Christians then took it a step further into what we currently consider science. Without the Arabian cultural merging with the other peoples of the Near East and Persia, the Muslim civilization would not have been possible. And without the mixing between Near Easterners, Northern African, Turks, and Iberian people, there would have been no Western civilization resembling anything we have today.
But even this account is very shallow. You have to look at an even larger picture. Humanity started out in one spot, with one culture and one set of ideas, and then others culture, religions, and languages emerged as they spread across the world. During that early hunter gatherer state, multiculturalism did not exist. That was the only true time where multiculturalism was not really possible over human lifetimes because of the limited population and technical means. Everything that happened after that point was a product of multiculturalism. The people who congregated into the first cities were merging their tribal cultures into a newer, more powerful one. Cities establishing spheres of control over their neighbors, forming city-states, was another form of multiculturalism. And so on. At no point was the cultural identity the same before as it was after the transition. The nomads that roamed Mesopotamia had nearly nothing in common with the eventual culture of Babylon, even though they were the ones who formed it.
And now with the advent of the internet, we finally have the seeds of a human culture at a planetary scale. That's why you're as concerned with Pakistani children as you are with French journalists. And that is why nationalist sentiment is at its lowest point in much of the developed world. The other day, I asked my co-workers a simple question; when was the last time you had the thought that you are an American? It is just not that important a consideration to most people. And I would like to see this continue, because it is of great benefit to humanity.
All I'm asking you to consider is if you really do believe in cultural segregation. As in, do you honestly believe that we should take a snapshot of the status of human cultures at this point and time, and then try to artificially enforce the status quo? For me, if countless division, endless stagnation and stunted species-wide growth is the only solution for something as trivial to the big picture as militant Islam, then we might as well let them take over, because we've already lost.