What is the ruling on limiting the call to Islam to refuting those who attack the fundamentals of the religion and mock the Shari'ah?

Question:
He says: If a student of knowledge has mastered the issues of tawhid (the oneness of Allah) and 'aqidah (creed), and then wants to specialize in refuting those who attack the fundamentals of the religion and mock the Shari'ah, is this direction good?

Answer:
Yes, he should refute them in the area he has mastered and knows, and it is not limited to this. It is not restricted to forbidding haram (forbidden) things; forbidding includes many matters, such as forbidding shirk (associating partners with Allah). But if one focuses on forbidding haram things and leaves shirk, which is the greatest of haram things, that is not what is forbidden. People say, "We are free in our creed and free in our religion." This is a contradiction, and may Allah protect us from it. Yes.