There will never be a time for mass censorship. Porn can easily be found online and off, same for drugs, and other horrible things if that is truly what on is looking for. Employers should be able to block the internet during work hours for employees using company computers when their jobs do not require the internet.
However, one of the most dangerous things that the internet can easily afford comes from REPUTABLE sources. That thing is accurate information. This is the reason that countries like China censor the internet to ensure that massive numbers of people don't rise up and demand the truth and more from their government.
Who decides whether or not IP providers have been operating for the sake "of the greatest public good?" Would this be done by a chosen few or worse, a single individual, that would benefit from keeping others in the dark and limiting the mobility of TRILLIONS of dollars worth of transactions carried out completely online?
We have many in politics that don't operate for the sake of the greatest public good and people VOTE them into office. Further, whenever individuals and large groups of citizens allow their freedoms to be stripped in the name of protection or safety, nothing but headaches and more bureaucracy is introduced in it's wake.