“Joseph- the people who could call out the fake tzadikim are the real ones because they have credibility. ”
JJ2020: This Mitzvah is a Mitzvah for everyone to do, not just a mitzvah only for tzadikim to do. Nowhere in the Mitzvah does it say that only tzadikim should do this mitzvah.
And make no mistake about it, doing this is a Mitzvah. The Chofetz Chaim tells us all about the severity of Loshon Hora, he also tells us — all of us, not just tzadikim, have this mitzvah. At the end of Shmiras HaLashon (Hilchos Rechilus 9:15), the Chofetz Chaim writes that the prohibitions against Lashon Hara and Rechilus do not apply to reshaim and kofrim and that it is, in fact, a mitzvah to mock such persons:
“מצוה לפרסם דעתם הכוזבת לעיני הכל ולגנותם, כדי שלא ילמדו ממעשיהם הרעים.”
“It is a mitzvah to make their false opinions public before all, and shame them so that others do not learn from their evil deeds.”
That’s the Halacha for you, for everyone here including me, for everyone in your shul and for tzadikim equally.