I think you have a good point, and I have the same opinion; Prohibiting something will not result in less use and abuse (alcohol, marihuana, abortion, euthanasia etc). In my country (The Netherlands) we are very liberal on these topics, however we do not have excessive usage and problems in our society with these things and freedom.
However, I do see examples in which the culture changes because of presenting more or less single messages. For instance: in Asia a lot of advertisement includes western (white) models which apparently contributes to the strong wish of a growing number of Asian people to be as white as possible (little to no sun bathing, wearing longs sleeves even when it sunny and 35/40+ degrees Celcius).
Another example is the increasing amount of teenager in the Netherlands (and accros the western world) with eating disorders such as anorexia; Apparently the numbers are increasing because of the so many bloggers/vloggers of teenagers with absolutely great bodies; bodies a lot of us are never able to get even if we would train 10 hours a day.
But said that: only proper research can give us an indication if one effects the other.
Some good reads on Internet, Blogging, Vlogging and resulted Eating Disorders: