It is compulsory for Ahl al-‘Ilm (the knowledgeable) to make a serious effort — more than Ahl al-Batil so that Ahl al-Batil will not outdo them — in declaring and calling for the truth wherever they are.
It is (also) compulsory for them to speak against the munkar and to educate with the best possible approaches and methods that are good, kind and soft.
It is (also) compulsory for them not to stay in silence against the evildoers, the heretics and the ignorants.
It is due to their silence that evil is spreading, that good thing is diminishing and disappearing, and that the Sunnah is fading away.
It is (also) compulsory for this move to be based on knowledge and insights, as a result of the help of Allah through the fruit of knowledge.
Source : Adapted from Sheikh Abdulaziz Bin Baz, Former Grand Mufti of Saudi Arabia.