Remaining silent about deviants is betrayal
It is not permissible for a Muslim who possesses knowledge to remain silent concerning deviant beliefs without clarifying it for the people.
This is because if he remains silent, the people will use him as an argument, saying, ‘if this was impermissible or prohibited, then the so and so would not have remained silent about it while he sees it.’
Allah, The Most High, Says:
“Those who conceal the clear (Signs) We have sent down, and the Guidance, after We have made it clear for the people in the Book,-on them shall be Allah’s curse, and the curse of those entitled to curse,-Except those who repent and make amends and openly declare (the Truth): To them I turn; for I am Oft-returning, Most Merciful.” [Al-Baqarah 159-160]
Thus, it is obligatory upon those who have knowledge to clarify the false matters. And they must prohibit and warn against the deviant sects, and not remain silent as remaining silent is considered concealing the truth.
Alhamdulillah Awaluhu wa Akhiruhu