It is obligatory upon you to explain the truth [concerning a group you know to be misguided and others may not know they are astray].
1. If you are sure about the errors that are with them [this group that you claim to be upon misguidance] and you are sure about the misguidance [or misguidances] that are with them,
2. [in addition you are] one-hundred percent sure that you have the ability [to refute them with appropriate evidences]
3. plus you have the knowledge by which you are able to clarify [their errors and correct them with authentic evidences to the Muslim public],
then this is obligatory upon you to do so.
Allah said, “And when Allaah took the covenant from those who were given the Book that you will explain, clarify it to the people and not conceal it.” (Al-Imran 3:187)
He also said, “Verily, those who conceal what we have revealed of clear evidences and guidance.” (Al-Baqarah 2:159)
It is not permissible to conceal knowledge. If you have knowledge with you and you are certain about the misguidance(s) of certain factions, then explain them to the people so that they may beware of them and this is from sincere advice.
He (sallallaahu alayhi wasallam) said, “The religion comprises sincerity of purpose”
And we (the Companions) said, “To whom?”
And he said, “To Allaah, His Book, His Messenger, the leaders of the Muslims and the common folk” (Muslim, no. 55).
Do not fear the people, upon you is to fear Allaah, the Sublime and Exalted and to explain the truth to the people, refute falsehoood and not to fear the people.”
Posted by Abdul Kareem Ibn Ozzie