Showing someone the Islamic ruling but they are not convinced

The second question of Fatwa no. 19172 All praise be to Allah Alone, peace and blessings be upon His Last Prophet.The Permanent Committee for Scholarly Research and Ifta' has looked into a request for Fatwa submitted to His Eminence the Grand Mufty (Islamic scholar qualified to issue legal opinions) by the representative of Da`wah and Guidance Center in Duba' No. A/135, dated 7/6/1417 A.H, and referred to the Committee by the General Secretariat of the Council of Senior Scholars, No. 3251, dated 17/6/1417 A.H. The questioner's inquiry reads:Your Eminence has earlier issued a Fatwa no. 18787, dated 3/5/1417 A.H, that rendered the act of a magician as Haram (prohibited), but some people were not convinced of that, let alone the magician himself. Does his sin become greater? Please support your answer with evidence, given that he does not have enough knowledge to say what is Halal and what is not.

(Part No. 1; Page No. 272) After examining the issue, the Committee answered as follows: Some people discern the Shar`y (Islamically lawful) ruling which is based upon evidence from the Book of Allah and the Sunnah of His Prophet (peace be upon him) but do not abide by it. They may do this out of arrogance; they may be sinners and should immediately repent sincerely. If someone finds anything dubious or can not fully grasp the evidence, they will be entitled to repeat the question to knowledgeable people and scholars to clarify it and make it understandable. However, once the truth becomes discernable for the questioner, it is obligatory for him to abide by the Shar`y ruling, even if it goes against the desires and whims of his own self.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.