Musar על מגילה 55:8

לא תקום . The prohibition against revenge or grudge-bearing (19,18) is based on the principle that a holy nation cannot relate to someone with hostility. Bearing a grudge in one's heart will ultimately result in acts of revenge. When a Torah scholar has been publicly slighted he must not ignore such a slight since the insult was directed at the Torah he represents. The Talmud relates that Mar Zutra the Pious forgave everyone who had caused him pain. The commentators explain that this referred only to physical pain or curses directed at his person. No Rabbi has the right to ignore insults that were directed at the Torah which he represents. Our sages (Yuma 22b) go so far as to say that any Torah scholar who does not take revenge like a snake is not worthy of the title "Torah-sage."