A book by Stephane Charbonnier, known as Charb, the late editor of the Paris-based satirical magazine Charlie Hebdo has been published posthumously and went on sale yesterday, the BBC reported.

According to the publishers Charbonnier finished the book only two days before he and eleven other journalists were killed by Islamic militants during an editorial meeting in January. The attackers, brothers Said and Cherif Kouachi were later shot dead by police.

In the book titled An Open Letter to the Fraudsters of Islamophobia who Play into Racists’ Hands, Charbonnier criticizes French society for neglecting the fight against racism by focusing on preventing Islamophobia.

He denounces Islam’s exemption from criticism and humor as “white, left-wing bourgeois intellectual paternalism,” in a staunch defense of Charlie Hebdo’s controversial content.

“The suggestion that you can laugh at everything, except certain aspects of Islam, because Muslims are much more prickly that the rest of the population—what is that, if not discrimination?” he writes.

Launched in 1969, Charlie Hebdo has satirized conservatism and all religions. Its below-the-belt satirical style has often made the publication a target of Islamic extremists. In 2006 it received death threats for publishing cartoons of the Prophet Muhammad. In 2012, the offices of the magazine were firebombed.