A: I advice them to learn first in order to be quite sure whether a matter is Ma'ruf (that which is judged as good, beneficial, or fitting by Islamic law and Muslims of sound intellect) or Munkar through the Shar'y (Islamic legal) proofs, so that when they raise there objections, it is done with insight.
Say (O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭ ﺳﻠﻢ): "This is my way; I invite unto Allâh (i.e. to the Oneness of Allâh Islâmic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allâh i.e. to the Oneness of Allâh Islâmic Monotheism with sure knowledge). And Glorified and Exalted be Allâh (above all that they associate as partners with Him). And I am not of the Mushrikûn (polytheists, pagans, idolaters and disbelievers in the Oneness of Allâh; those who worship others along with Allâh or set up rivals or partners to Allâh)."
Invite (mankind, O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭ ﺳـﻠﻢ) to the Way of your Lord (i.e. Islâm) with wisdom (i.e. with the Divine Revelation and the Qur'ân) and fair preaching, and argue with them in a way that is better.
"Whoever is deprived of kindness is deprived of all good."
"Kindness does not become a part of anything without adorning it, and is not withdrawn from anything without marring it."
The Da'y (caller) to Allah, the enjoiner of Ma'ruf and the forbidder of Munkar should be the first to practice what they preach, and the first to abstain from what they order people to avoid.