Why is slandering a chaste non-Muslim woman not considered a major sin, even though it is an injustice and a false accusation, and Allah Almighty says: "And those who accuse chaste women..." and He did not say "believing women"? And what is the response to the claim of racial discrimination that enemies of Islam raise based on this?

Slandering a non-Muslim is forbidden (haram), and the one who commits it deserves discipline (ta'deeb) and discretionary punishment (ta'zeer). Scholars have differed regarding the obligation of applying the prescribed punishment (hadd) for it, and whether it is a major or minor sin. The majority (jumhoor) hold that there is no hadd for it. However, the Zahiriyyah consider the hadd obligatory, and Ibn Hazm regards it as a major sin, citing the generality of the verse on qadhf (slander) to include both disbelieving and believing women. As for the specific qadhf that necessitates the hadd, it applies to Muslims according to the majority of jurists. Regarding not initiating salam (peace) with Jews and Christians, this does not prevent greeting them with another appropriate greeting. Salam is a symbol of Islam and one of the names of Allah, carrying meanings befitting a Muslim, not a disbeliever. A Muslim should have certainty in their religion, for Allah Almighty is truthful in His tidings and just in His judgments. Focusing on faith and introducing Allah when engaging with non-Muslims makes it easier for them to accept the rulings of the religion.