IstIfta Regarding the Prohibition of Registering in Facebook

Question:
A group of brothers and sisters has written in their numerous letters: we will be thankful if Ayatollah Makarem Shirazi explains the reason behind the prohibition of registering if Facebook. This will answer the questions of people who ask this.
He said in answer:
My dears; the reason is clear; this is a tunnel to spread corruption and many kinds of sins widely among the society.
Since Facebook is like an uncontrolled city that everyone from scientists and elites to thieves and swindlers and those with various types of corruptions, has a shop in this city. In these stores, sometimes, the necessities of life and in many cases the instruments of sins and corruptions and moral deviations as well as instruments of creating disputes among nations with beautiful labels and glamorous covers, are available for all.
Now, if all people from youngsters to unaware adults be able to enter the city easily, then, can any informed person leave everyone to enter this city freely?
Even spies and corruptors on earth can exchange information in this city and do conspiracies with some codes and signals. We say that there should be a general supervision on press and media to prevent people who are corrupted and corruptor from infecting community in this way.
Yet why should Facebook be free unconditionally? Do we have Unconditional freedom in this world? Some of the Western limitations do not solve the problem anywise and duplicating the problem is not solving the problem.
Yes if only vigilant and educated people, who can completely understand good and evil and distinguish pure from impure, could enter the city just for social researches, it was no problem. Such as the misleading books which scholars forbid people to study them but religious researchers are allowed to read them.
The Office of the Ayatollah Makarem Shirazi