The gemara says that one who is machzik a machlokes is in violation of a negative commandment - ולא יהיה כקרח וכעדתו. The gemara says that it is for this reason that Moshe went to speak with Dasan and Aviram. It seems from the gemara that the issur of not being machzik a machlokes obligates one to take action to avoid the machlokes. Rashi seems to say this - מכאן שאין מחזיקין במחלוקת - שמחל על כבודו והוא עצמו הלך לבטל מחלוקת
The fact that Moshe Rabbeinu was willing to be mochel on his own kavod to confront dasan and aviram implies that one is obligated to take action in order to avoid machlokes.
The chofetz chaim (pesicha, l'av 12) points out that the Sma"g and Rabbeinu Yona seem to consider this an actual l'av. He considers the fact that there may be an obligation on the listener to show contempt at the teller for saying over the loshon ho'rah to avoid this l'av. Although he doesn't cite rashi, perhaps he understands from rashi that there is an obligation to take action to avoid machlokes.
In his sefer Shemiras Halashon (sha'ar ha'zechira #15) the chofetz chaim suggests that one who takes an oath to join with a group that is creating a machlokes, would constitute a shavu'as shav since they are in essence swearing to violate a l'av in the Torah. Although none of the counters of the mitzvos (Rambam, Ramban) count this as a l'av (other than sma"g and Rabbeinu Yona), it is still clear from the Torah that it is forbidden and no worse than swearing to violate an issur of chatzi shiur which would also render the oath a shavu'as shav. The difficulty with this approach is that און בן פלת had to figure out a way to avoid violating his oath (bottom of 109b) - why? His oath should never have been binding since it was to join machlokes? The Chofetz Chaim suggests that און didn't yet to teshuva, he was merely following the logic of his wife that either way he will be a nobody so what is the difference whether he is subject to Moshe or Korach. It is only later that he realized the mistake and did teshuva. From here we learn that the merit of the wife of און בן פלת is not just that she saved her husband. Rather, she came up with a tactical approach to play on his ego and prevent him from joining. It was only later that he actually did teshuva l'sheim shamayim.
The Rambam in Sefer Ha'Mitzvos (shoresh 8) says that this l'av should be counted because it is not a command, rather it is a consequence that if one argues on kehuna he will get tzara'as. The Ramban disagrees saying that it is an es'machta. See Meshech Chocham (17:5) who explains the opinion of the Rambam that it is a "shelila" - a consequence or cause and effect, meaning that to avoid suffering a similar fate to Korach, one should not be like Korach.