If you incite violence against a specific group using a specific platform then yes, the publisher has some degree of responsibility for that. What's wrong about that observation?
He just told you what's wrong. It's like putting the blame on the messenger. People need to take responsibility for their actions rather than blame the platform for allowing it to be said. How about you don't say it in the first place? What are we going to do next, ban the air because it enables some bad people to tell and shout their violent opinions and transmits sound pressure waves?