Aveirah, look up what meforshim say that means.
The Riva says the left/right mentioned in the pasuk refers to Rabbonim telling us not to do a mitzvah such as Shofar on Shabbos, or Arba Minim on Shabbos. It only refers to a mitzvah that they are telling us NOT to do.
The Yerushalmi says in Horios that the pasuk means only if they say right is right and left is left. If they say otherwise, you do not listen.
There are many shitos against Rashi. Indeed, both Rambam and Ramban do not pasken like Rashi in this regard. There is a Sifre which Rashi bases it on, but again, many question the Sifre, and there are Gemoros in both Bavli and Yerushalmi that say otherwise. R’ Ovadia Yosef reconciles the two views as I mentioned above – you have to confront the Rav if you think he erred. Until you confront him, you do not listen. The Yad HaMelech states that if you listen when you think he erred just because you think you have to listen, you are required to bring a korbon chatas. Only after confronting the Rav with the opposing view, and he stands by what he said, are you required to listen.