Nor do I intend to repeat again the Suras that ban the use of compulsion, call for dialogue and urge people to get to know each other. I have already quoted them in articles of other chapters. I remain solely on the theological basis of the Quran.
I'll start with an etymological explanation. In the thinking of western cultures, the word struggle and war are often there. Class struggle, evolutionary struggle for the survival of species, the strong wins, the weak fails, and etc. The meaning of the words and expressions reflects strength and violence. If that’s the vocabulary, that’s how thinking becomes. This attitude can also be perceived from the title of Samuel P. Huntigton’s book “The Clash of Civilizations and the Remaking of World Order”. The title alone makes us feel the image of a huge fight. One has to win and the other has to be destroyed.
I do not find such a meaning in the words used by the Quran. There are words describing wars, struggles, jihads in defense of good and against evil. However, in terms of ethnic groups, civilizations, cultures, I cannot find an example where these or the synonyms are used: “clash, the better should win, one devours the other.” It is there e.g. that believers should not give way for unbelievers, but it means that they must protect themselves in order not to be attacked. It doesn’t direct them in the sense that a tight siege has to be drawn around the unbelievers, that they can’t even move. No expressions can be interpreted as an assault to outward. It’s also there to kill them, but it also applies only to attackers. These words are used specifically in times of aggression. The characteristic term which is used in the Quran in the course of coexistence of different people is the protection and providing protection one another. The word is تدفافع ,دفع dafa’a, tadafu’a, i.e. defense, protection. It calls the strong to protect the weak. Nothing can be forced from the side of superior to the weak.

…And did not Allah Check one set of people by means of another, the earth would indeed be full of mischief: But Allah is full of bounty to all the worlds. (Quran 2:251)

And as for Sharia, it calls everyone for following his own Book. Book also means law, as in the case of Muslims, the Book is not a psalm prayer book but doctrine and law. The next verse assumes that something similar is available to everyone and refers to this:

To thee We sent the Scripture in truth, confirming the scripture that came before it, and guarding it in safety: so, judge between them by what Allah hath revealed, and follow not their vain desires, diverging from the Truth that hath come to thee. To each among you have we prescribed a law and an open way. If Allah had so willed, He would have made you a single people, but (His plan is) to test you in what He hath given you: so, strive as in a race in all virtues. The goal of you all is to Allah. it is He that will show you the truth of the matters in which ye dispute; (Quran 5:48)

The general meaning is that rules and regulations which can be implemented worldwide are of Divine origin. When men enter and fabricate, manipulate these laws and think that man-made constitutions and national jurusdictions are better than Divine laws it is a matter of time and men will fail. It happened with Jews, Christians and we Muslims are not free of that mistake, too. In our case there is an additiona issue. We are going to implement literally a Divine law wich is above the dimension of time and space and we link it to an earlier age. The Quranic Laws as other Divine Laws are general and provide us frames in order to work out the details in every age and region. They cannot be violated by linking them to a specific age or region permanently and implenting them as obligatory this way. By origin mankind were a single people or nation: 4:1, and 2:213. That being so Allah could have kept us all alike, with one language, one kind of disposition, and one set of physical conditions (including climate) to live in. But in His wisdom, He gives us diversity in these things, not only at any given time, but in different periods and ages.

As for the classical teachings of Islam, it not only allows pluralism, i.e. the coexistence of civilizations, but considers it natural and issues statements in this regard. "Clash" is not foretold by Islam among civilizations, but is proclaimed between the destructive forces of Gog and Magog, Dajjal on one side and Mehdi, Jesus and their followers on the other side. Yes, we use such words here in our Books, but not regarding peoples, cultures, civilizations.
On a religious basis, therefore, pluralism in Islam is to be welcomed. What is the reality after all? It is different. I can't comment on that. Reality is related to human weakness, ignorance, pride and not to the word of Allah. This is the case in our side and elsewhere.
Gog, Magog and Dajjal are not interested in affiliations.