The Mishna in Pirkei Avos states that a machlokes - "a dispute" that is for the sake of Heaven will ultimately endure. Hillel and Shamai are given as an example of such a dispute. Why should we want any dispute to endure? The recorded example of a dispute which is not for the sake of Heaven is referred to as "Korach and his henchmen". Why does the Mishna not use parallel language reflecting both disputants, Korach versus Moshe, as it does in the example of Hillel versus Shamai?
Korach's argument is that all Jews experienced the sanctity of Hashem's revelation. Why should the position of Kohein Gadol not be open to a rotation that allows equal access to all Jews? Moshe takes the position that only one individual can be appointed and it is his brother Aharon. It would appear that Moshe's stance is the more divisive one. Korach is expressing the notion that all men are equal. Why is Korach labeled as the quintessential Ba'al Machlokes for posterity?
True unity can only be achieved if each individual is respected for his own unique abilities and perspectives. Only when we are different can we complement one another. If we are carbon copies, true unity will not be achieved for each individual will be concerned that he can be replaced.
Dispute itself is not necessarily negative; the Talmud, which represents the entire corpus of Jewish law, is comprised of conclusions derived from disputes. Dispute sans personal agendas allows for various perspectives to be expressed. These perspectives are necessary and should endure for they complement one another in the pursuit of truth. Korach's position that each person can be replaced is divisive, and the Mishna expresses this notion as if he is actually competing with his own henchmen. It is very common that when members of a dissenting faction are driven by personal agendas, they will often turn on themselves, for they are not truly unified; they just happen to share a common objective at that point in time.