I'm not sure how posting on a social media platform is any different than going to a bar and talking to strangers or standing on a corner and handing out flyers other than it being easier.
They don't hold the bar or restaurant responsible for the conversations that happen there, Motorola was never held responsible when Thier products were used or misused to communicate during crimes.
Instead of looking for scapegoats we should be educating kids, improving the middle class and teaching acceptance of our differences.