Lots of people are killed by alcohol, why is it not banned already? Lots of people are killed in cars - let's ban them. You are not eating healthy, not enough vitamins and nutritions? Put you in jail!
Tragedies happen, but why can't we live with them and try solve the causes instead of results? How many people read the manifesto written by the killer? I don't agree with any brutality but there are some points to think about.
If they ban one service, they will use another one next time. Or people will watch it from an archive. Or they won't watch the it at all and trust news blindly.
But the censorship will harm everyone. It will force people to post positive, optimistic posts only. It will control what is good and what is bad. It will present a fake ideal reality.