Very tough question. We all know what happens when you give the government an inch, miles later you wish you hadn't.
Although there is a point where a "violation" occurs. If a parent can't get up and make popcorn without having to worry that his 8 year old is going to be presented with a situation where a nasty whore is having sex with a horse, well we have a problem. Adults choosing such is one thing, kids are another.
There's a point where "turn the channel" doesn't cut it. Keeping certain types of programming away from your family shouldn't have to be a full time job.
The cat may be out of the bag, because you're question of "how" to regulate such is extremely difficult to answer. The government will just screw it up as they do everything else.
I guess my answer would be a rare "I'm not sure." It would probably be a combination of government on a short leash, an active private sector and good parenting, along with the recognition of the difference between subscription programming and public airwaves.