How can the preacher be helped to purify himself and adhere to the methodology of the Sunnis and the Community, especially since he had illicit relationships and belonged to a dissenting group?

You should only accept to marry a man of religion and good character, according to the Prophet, peace and blessings be upon him, who said: "If someone whose religion and character you approve comes to you proposing marriage, then marry him. If you do not do so, there will be tribulation on earth and widespread corruption." If the suitor holds beliefs of disbelief or insults the Companions, beware of marrying him, and seek out righteous young men from the Ahl al-Sunnah (definition).