The vast majority of drug users do not have problems (almost every adult uses drugs) except problems with the legal systems.
This is well known and extensively documented. I would encourage you to study what has happened in Portugal over the last decade.
Different drugs have different effects. Alcohol is one of the more dangerous yet is legal and a huge business. More dangerous than cocaine, heroin, ecstasy.
See David Nutt's research from the UK.
http://www.businessinsider.com.au/alcohol-more-harmful-heroi...
http://www.sciencemediacentre.co.nz/2010/08/06/professor-dav...