Of course they are not responsible for the actions of the shooter, or anyone who decides to use violence to make their point. They are partly responsible for the mounting rage at their increasingly arbitrary treatment of users, and near-total lack of transparency about it, which has been festering for years, and is getting worse. They are quite responsible for those arbitrary decisions themselves. What's that bit about freedom not implying freedom from consequences? These things are related. 'Victim blaming' and other thought-stopping catch-phrases aside.