Social media websites should be held responsible for the content on their sites. It is similar to a newspaper being responsible. Terror victims are suing Twitter for spreading ISIS propaganda. Twitter has a responsibility to be a good corporate citizen and not facilitate terrorist messages. These sites should be forced to report this activity to the authorities.
It is tricky for Twitter because with the huge volume of users they have, and subsequent tweets, how do you effectively police that? They are making an effort and lots of accounts are getting closed down, but they won't get them all, some will stay up for weeks or even months. They have to shoulder a bit of the blame, but they shouldn't be sued.
No, Twitter is not responsible for ISIS propaganda spread on their site. The company provide a platform for social media interaction. They cannot be responsible for all of the images and language spread using their platform. Within reason, they should uphold their own restrictions and guidelines but no one can blame them for the actions of others. No one sues a car company for the reckless drunk driving of some users.
Look, let's call this what this is. Social media is not responsible for ISIS propaganda. This is nothing but a money grab by the families, in particular cash hungry lawyers, you look for any and always to make a quick buck. This lawsuit is absolutely shameless, and this example A1 why we need a loser pays systems.