[Symmetry]

It's a complicated issue which, as far as I can tell, mostly comes down to whether illegal drugs tend to displace alcohol use or not. If someone who regularly uses alcohol to become intoxicated switches to weed that's a big public health win. If they use weed in addition that's a public health loss. If they switch to heroin they're clearly worse off, but they're less likely to harm others due to drunk driving or induced belligerence.

A couple of independent harm analyses: http://welshcouncil.org.uk/english/dangerlist.html http://www.economist.com/blogs/dailychart/2010/11/drugs_caus...