Sheikh Zaid Bin Haadee Al-Madkhali (hafidha-hullaah) said:

It is not permissible for the one who knows something concerning the innovations of Ikhwaan Al-Muslimeen (The Muslim Brotherhood- illegal partisan group) or other than them amongst the people of innovation and error that he remains silent about clarifying (their affair), whilst he has the ability to clarify; because refuting the people of innovation and errors is obligatory upon those who have the ability to do so from amongst the People of Knowledge. And when it is established by some of them, the obligation is lifted from the rest.

As for fearing splitting as a result of refutation against the sects, then there is no legislated Islamic excuse for refraining (from such); because having love for unity (upon the sound creed and methodology of the salaf) is what is correct and more deserving to be desired and followed. The innovator is the cause for the splitting in the Ummah; because splitting is connected to innovation and unity is connected to the Sunnah.

And the obligation of refutation against the Mukhaalif (the one in opposition to the truth) is not lifted from the scholar due to anticipation of harm, unless it is harm he is not able to bear; then (in this case), Allah does not burden a soul beyond what it can bear. The earth is not devoid of people of knowledge to carry out refutation against the innovator and the one in opposition to the (truth).

[Source: Al Ajwibah Al Mukhtasar Alaa As-ila Al-Ashrati Page43-44]

Abu Mu-aawiyyah (Abdullaah Al-Gambi)