It's not censorship, it's classification - which I'm all for.
There has to be age restrictions on violent and sexy material. Would you like a little boy terrified by the grim horrors of
Haute Tension,
Saw or
Wolf Creek?
Teenagers are always going to complain, since teenagers want to be classed as adults. But, like it or not, until you are an adult your parents and The State are responsible for you.
So be resourceful - like someone just said, give a bum a bottle of cider from your parents' cabinet and ask him to buy/rent stuff for you.