About the duty of social networks: What will be prevented by the censorship of these hateful messages?

 

Nothing. The only duty of social networks is to answer properly to the request of police and Justice if a verbal threat was followed by any damage to some people or to its goods. And BTW justice for these damages should be very strong. Because the perpetrators if identified as author of one of tehses messages acted with premeditation.

More generally I didn't heard about public post administration accusation for handling and shipping parcelas with illegal drugs, weapons or theft goods...
While free speech is a fundamental right, it is also a component of an effective state that prioritizes compensating victims. every one understands that a state which is unable to eradicate terrorists is by far un able to indict the (millions) of French citizens or residents which spill their hate on social networks.