Is it permissible for a Muslim to mock and ridicule a disbeliever?

It is not permissible to mock or backbite a Dhimmi (protected) or Mu'ahid (covenanted) non-Muslim. This was affirmed by Al-Ghazali, Ibn Hajar Al-Haytami, and others, who based their rulings on the hadith: "Whoever hears a Jew or a Christian (being maligned), for him is the Fire," meaning whoever harms them. As for the Harbi (belligerent) non-Muslim, backbiting or mocking them is not forbidden, as maintained by Al-Ghazali, Ibn Al-Mundhir, and Zakariya Al-Ansari. Al-Razi further supported this by citing the verse: "Would any of you like to eat the flesh of his brother when dead?" (Qur'an 49:12), where backbiting is likened to eating the flesh of a brother, and brotherhood exists only among believers. However, this permissibility is conditional on the mockery or backbiting being truthful, not false, and that it does not lead to corruption, such as harming Muslims or ridiculing Islam. It is preferable to abstain from such actions and instead busy oneself with what benefits Muslims.