English Explanation of Pirkei Avot 5:17

Every dispute that is for the sake of Heaven, will in the end endure; But one that is not for the sake of Heaven, will not endure.
Which is the controversy that is for the sake of Heaven? Such was the controversy of Hillel and Shammai.
And which is the controversy that is not for the sake of Heaven? Such was the controversy of Korah and all his congregation.
This mishnah discusses legitimate and non-legitimate disputes. While reading the mishnah we should keep in mind that the Mishnah is the first Jewish book which records disputes between different viewpoints without claiming that one viewpoint is necessarily illegitimate. 150 years before the Mishnah was composed, Judaism had certainly been rife with disputes which caused splinter movements, such as the early Christians and the Dead Sea sect. Part of the overall goal of the Mishnah’s composers was to say that sages can disagree and still live together. We will soon see a classic exmple of this philosophy when we begin to learn tractate Yevamoth.
In Judaism debate is legitimate. Indeed Jews are famed worldwide for being an argumentative people, and this is considered (at least by most Jews themselves) a positive attribute. What is problematic is not debate itself, but debate that does not attempt to reveal the truth, and especially God’s truth. Debate that is only self-serving, an attempt to be victorious over the other side is considered to be illegitimate. The debate that is for the sake of Heaven, which stems from a desire to seek the truth, will endure. The classic example of this are the debates between Shammai and Hillel. This debate endured in several ways. First of all, in the time of the Mishnah, there were probably still scholars who followed Shammai. The debate literally endured, because scholars were still arguing about who is right. Second, students of the Mishnah and Talmud continue to study the debates of Shammai and Hillel. Although by the time of the Talmud law usually follows Hillel, the debate endures as study material throughout the generations.
Korah and his congregation rose up against Moses’s leadership in Numbers 16. Their intent was not a pure complaint against the perceived autocratic style of Moses’s leadership. Rather it was a blatant attempt to gain power for themselves. As our mishnah teaches, it was not a dispute for the sake of Heaven, but rather for their own profit. Therefore, the dispute did not endure, for Korah and his congregation were all wiped out (either by the earth swallowing them or by fire).
Note that the mishnah does not say “the dispute of Moses and Korah”, but rather only mentions Korah and his congregation. This is in contrast to the previous section where both Hillel and Shammai were mentioned. This discrepancy is because Moses and Korah were not operating out of the same motives. Moses disputed with Korah not for his own glory, but for the sake of Heaven. Therefore the mishnah could not mention them together.