For the technophobes, Virtual Reality is here. All you have to do is strap on a mobile phone to your head and your in a universe of make believe.
How can the virtual be policed? The short answer, it can't. It's impossible. Unless every human being in the real world is in prison. How is that possible? Your very own Robot police-droid watching everyone's every move.
This is the solution to the problem. Would you want that solution? To be imprisoned by robots, making sure everyone followed the rules of law day and night? For the small price of freedom, are we to accept such vulgar expressions of our freedom?
How vulgar does imprisonment look? Both ends of the spectrum can be pretty gross. Dystopia versus things you wish wern't there. While you will never be forced to view anything you don't like, be happy that your own preferences, no matter how distasteful other people find them, will be permitted.
This is as simple as it gets. 