End Demand doesn't work. That's not a moral statement - it's a literal fact. Look at The Prohibition. Look at The War on Drugs. I understand that some people have moral beliefs against things like drugs and alcohol (or pornography and prostitution), but it's not the government's job to legislate morality. Unfortunately, people with an "everyone ought to believe what I believe" mentality have a tendency to actually believe that people who don't live the way they do deserve to be punished - to either be forced to change their ways, or be thrown in jail.
That's not freedom. The laws we have in place are not there to dictate what kind of lives we should lead, so as to force society to become a certain kind of environment - the one admired by the moral majority. No. If we value freedom at all (and I don't think many of us do in this day and age), we must permit others to pursue their individual paths. We have laws to protect people from harming other people, and infringing on the basic rights of others. Forcing other people to live like you do and think the way you do is NOT a right that anyone possesses!
So if it's true that people have a hunger for illicit substances - like mind-altering drugs or pornographic liaisons or what have you - what can we do? Putting up a fence between the people who demand these things and the people who supply them isn't right, because it involves the restriction of individual liberty. But you can disagree with that statement - what you can't disagree with is that, whether right or wrong, it simply. doesn't. work. Instead of fostering an us vs. them mentality, the puritans vs. the depraved, can we not be more forgiving of each other's differences?
If there are dangers in one way of life, then the compassionate thing to do is to educate, and support - additionally, you can apply subtle persuasion, but only that which does not involve forcibly changing another person's life against their wishes. If there are arguments against your way of living, you should consider them, and at least allow them to be aired even if you don't agree. There is enough room in this world for people of all kinds. If you don't like drugs, or you don't like sex, you're welcome to construct a life around yourself that doesn't involve drugs or sex. Meanwhile, another person should remain free to construct his life around drugs and sex if he so chooses - without your interference. Why must everyone in the world live like you do?