Multiculturalism in General
Many people believe in universal group unity where all humans under the right social conditions can live in peace and harmony with no occurrence of violence hatred or suffering. All human divisions, they believe, are caused by irrational hate and malice that is generated by ordnance and so the only way forward for humanity is the amalgamation and unity of all humans in one place which will eventually lead to a sense of universal love among all humans where world peace will finally be achieved.
The very project of human amalgamation is what's also known as multiculturalism which is a grand experiment that takes in youthful individuals from any part of the globe and makes them settle in one place, such as a country, where they are expected to use the new opportunities of their new country to improve their own living conditions and integrate into society along with every other new arrival with the final result being a country where all divisions between them4eselves and those who live among them have become nonexistent.
This very dream of universal human integration is something that someone with a lack of understanding of human nature would conclude as they know why humans ha divided themselves in the first place as well as why humans are constantly fighting, exploiting, and hating each other. This very lack of understanding of human nature is also why many people don't realize that multiculturalism is an inevitable failure that was caused by human nature itself.
Homogenous vs Heterogenous
Why does crime exist despite the existence of human groups which are meant to fulfill the needs and desires of every individual in their midst? While differences in morality are certainly one of the reasons for the existence of crime; another reason is the fact that human groups, to properly be solid cohesive entities all aspects of human groups, such as language, culture, social values, and even ethnicity need to be the same or similar. This cohesiveness among human groups, in fact, has been achieved before during early human history when local humans, after having settled and adapted to their new environments, began forming similar languages, cultures, religions, and varieties in bodily function and appearance due to natural selection. These new human groups would have initially been quite cooperative and friendly with each other when they settled, worked, and shared resources with each other.
This cohesiveness can even be possible even when a human group is highly populous and spread out over large cities and towns where they are the sole inhabitants of said places of habitation. The main aspects of a group that actually maintains group cohesion would be 1)Culture, 2) Ethnicity, 3) Religion or Communal Morals, and 4) Language. The reason these very aspects of human groups seem to hold the group together is that these aspects apply to large regions of people that are spread out over wide areas which explains why large swaths of the world have people who have similar languages, religions, and cultures to get along with each other whenever they meet such as two Spanish speakers who come from two different Latin American countries or when two Muslims from Africa and Asia meet.
Also, when it comes to ethnicity or race, which is really just similar varieties of people that fall into quantitative categories, the existence of a common appearance among a group reinforces and aesthetically represents the group’s homogeny as well.
But when human groups that have different cultural, linguistic,, religious, or ethnic backgrounds meet each other one of two things can happen. Either these two groups, if there is some resource or benefit that both groups want from each other, will cooperate with each other for mutual group benefit or they will start conflicting with each other because either group wants resources and land that the other group wants and vice versa for the benefit of either group at the cost of the other. This very inevitable kind of conflict between human groups is why human groups separate themselves through borders between them. But when human groups break these borders in an attempt to unify both groups; this very conflict will arise again.
However, human conflict, through breaking borders, plays out very differently from usual human conflict which is often expressed through war. This conflict expresses itself when an individual or a smaller group from the main group they came from arrives and finds themselves unable to attain the resources and land they came for through conventional means that have been set up by the other group which was designed only to benefit the aforementioned so the initial group will either turn to crime both organized or unorganized to undermine the already set up systems of laws, customs, values, and civil activity.
This undermining of the current system, with enough social pressure from both empathizers and members of the undermining system, will allow said group to finally gain resources and land for themselves and finally function as a people. However, because human groups are always looking to grow and gain more resources for their group’s benefit; they will continue to undermine the system that gave them their initial benefits until that system has been toppled and replaced by their own systems that are meant to benefit them and the cycle will repeat should another group come in.
The fact that human groups are always looking to benefit themselves, even at the cost of other groups, is why a heterogeneous group that is formed from migration towards a certain part of the world is bound to not get along with each other and when they are made to live under one government or country frequent disagreement and different group goals will always cause crime, discontent, and civil chaos to occur until one group out of the many emerges victorious and dominates the rest of the groups. But if this doesn't happen then the crimes and other forms of conflict between human groups will remain.
So, overall heterogeneous groups will often fight with each other due to conflicting group interests as well as individual interests because there is a lack of ethnic, linguistic, cultural, or religious unity among heterogeneous groups and this conflict between groups is often why human groups stagnate in their own development of their own people something which homogenous groups lack.
Race & Ethnicity
Homogenous groups, primarily form around common culture, languages, history, and sometimes religion,; many will agree that all these things, except religion in some cases, forms whats known as an ethnic group. Every country that exists or has existed has always been built around a certain ethnic group, except for empires, such as the Spanish, Chinese, Egyptian, etc. Numerous ethnic groups around the world are at least centered around one attribute of an ethnic group such as Latin America which predominantly speaks Spanish or the nations of the Middle East and North Africa which predominately speak Arabic except for Iran and Afghanistan which speaks Parsi and other related Persian languages.
But the human race, contrary to commonly-held beliefs, is not the same as ethnicity because races of humans are defined as a group of people with similar traits while ethnic groups are based on what is essentially the mental and social products of a group of people. Race on the other hand is based on the physical differences of said people. It is also worth noting that unlike race, which is genetically inherited due to the occurrence of said varieties, any human being, that has no predominate loyalty to another group, can become part of an ethnic group by learning the language, adopting the culture, and embracing the history of their adoptive ethnic group. Nevertheless, it does seem that ethnic groups and races seem to exist together in certain parts of the world. In general, ethnicity or ethnic group is the result of the mental production and social interaction of a group of people while race is the physical constitution of said people compared to other groups.
So basically, the reason why multiculturalism is an inevitable failure is due to the inevitable conflicts that will occur among human groups and unlike individuals because of conflicting interests or goals that are meant to benefit said groups and individuals. When human groups are homogenous, there is mostly a lack of differences among people in terms of their goals and identity which is why said people can work with each other towards a common goal whereas the opposite is true for a heterogeneous group or a bunch of unlike human groups who live near each other. So, if people believe that cultural enrichment and a lack of conflict are going to result from multiculturalism; then they certainly don't understand human nature and all of its aspects in an unbias way.