"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
The real reason is the left, after souring on Stalin, decided to make the colonial third world their new mascot noble savage proletariat. Starting with men like Fanon, they just decided that the non-white poor of the world were universally justified in anything against the evil oppressive capitalists of the north. They spewed that nonsense for 50 years and they built entire philosophy departments to justify it, though it was a nihilist embrace of barbarism and murder from the start. The chickens having come home to roost, they are in denial over the consequences. Which are their own speedy extermination.