Is speaking ill of the lineage of the Prophet's disbelieving relatives, such as saying that Abu Talib died a polytheist and should be hated for the sake of Allah, considered harming the Messenger in his lineage, especially in light of the hadith, "Every lineage will be cut off on the Day of Resurrection except my lineage"? And does the existence of disbelievers and polytheists in the Prophet's lineage contradict his being the best of people in lineage?

The summary of the Fatwa:

The Hadith "A Muslim should not be harmed because of a disbeliever" was narrated by Al-Suyuti from Durrah, the daughter of Abu Lahab. It is interpreted to mean protecting a Muslim from harm due to their lineage. It is not commendable to speak ill of the Prophet's disbelieving relatives except for a legitimate Shar'i purpose, such as clarifying that lineage does not benefit a disbeliever. The Prophet, peace and blessings be upon him, said: "Whoever is slowed down by his deeds will not be hastened by his lineage," meaning that good deeds elevate one's status, not lineage. Mentioning Abu Talib or others for a legitimate Shar'i purpose is permissible. The lineage of the Prophet, peace and blessings be upon him, is the best lineage absolutely. The honor of lineage does not contradict the presence of a disbeliever within it, because lineage is established in and of itself. The Ahl al-Sunnah wa al-Jama'ah believe that Banu Hashim are the best of Quraish, Quraish are the best of Arabs, and Arabs are the best of the children of Adam. This relative honor does not contradict the preference for pious individuals, as pious Arabs are better than pious non-Arabs when they are equal in piety. The statement by some, "All their lineage are Muslims," is incorrect, because there was no Arab lineage before Islam that did not contain those who were not monotheists.