Accurate marginalization...or unnecessary?

People are raised, educated, and exposed to a multitude of cultural environments all over the world. Therefore, there certainly are “differences” between them; this is a logical and obvious fact. However, even if a person from one cultural background recognizes another person's cultural background as different from his own, does he have the right to marginalize because he deemed it “different”? What knowledge must he have before he can appropriately marginalize or accurately distinguish another’s background, either directly in person or in discussions with others? A clear and objective consensus of the other's identity and culture, as he wishes to be known, must be made before another person has the right to make a particular distinction. Therefore, all people should be respected through a subjective reference to which they concede. When another disagrees with a particular people’s label for itself, it becomes a personal judgment, however, which does not qualify as an official marginalization because the subject may not be in agreement with such judgment.
However, are distinctions between groups of people always a necessity - do they have a purpose? There are many situations where it is entirely irrelevant and even inappropriate to make a point of noting certain differences. Often, in a politically correct argument, it is possible for a group of people to feel that a particular distinction or marginalizing remark is “derogatory.” A term is offensive if it attempts to challenge the equality of the subject based on irrelevant characterizations. However, if equality between people is presumed in a given situation (as it always should be), is there really a need to make distinctions between people? Isn’t it irrelevant unless the personal differences are of importance and should be taken into consideration because they may significantly influence the course of important events? For example, it would be wise for an American businessperson to be aware of the cultural differences before entering in negotiations with a Japanese counterpart, so as to not unwittingly offend him and risk losing an important deal. This is not to say a person should not feel free to celebrate his heritage and distinct cultural background, but rather to address situations where divisions would be unnecessary and would result in a separation of people and the building of walls, rather than bridges that would facilitate and enhance understanding.