On the contrary, illegality of drugs fuels crime. Make them legal and society benefits; the users may be damaged but that is their responsibility. If you really want to protect society as a whole then alcohol and tobacco should also be prohibited. Tobacco kills more people than all other drugs, legal and illegal, put together.I don't think the parallel with drugs is very good because there a reasonable argument can be made that it is a protection-of-society-as-a-whole issue whereas a similar reasonable argument cannot be made in respect of bicycle helmets. In any case the direction drug laws seems to be taking at the moment is the opposite, with quasi legalisation of cannabis in some US states now.
The problem is the more you nanny people the less prepared they are to think and look out for themselves.
I'm afraid I am at the other end of the spectrum on this one, Barry Heaven.
On your point about nannying people, for example, making seat belt use compulsory ensures that people look after themselves. They don't need to even think about it as it has become the norm.