Considering the attack in Charlie Hebdo, the possible reason is publisher’s repeated offensive satirical cartoon with deception of Prophet Muhammad, which is banned in Islam religion. Since the attack there has been controversies on whether that cartoon was hate speech or not. ISIS officially claimed criminal declaration.
Charlie Hebdo has been publishing satirical cartoons since 1970 and it hasn’t only been publishing some offensive ones towards Islam but also towards Africa, Asia, and US. According to The Guardian after the attack Pope Francis said that one cannot make fun of faith and also “There is a limit. Every religion has its dignity…in freedom of expression there are limits.” As Charlie Hebdo violated dignity and rule, and made fun of Islam, which is drawing deception of Prophet Muhammad, which is strictly banned, this cartoon could be considered as hate speech.
According to French Government, even though freedom of expression is supported by the Declaration of the Rights of Man and of the Citizen, public defamation and slander are punishable by law. The cartoon clarly defamed and slandered Islam as it offended Islam’s dignity and made fun of it. Therefore, the cartoon would be considered as hate speech.