Advocating that something should be lagalised does NOT mean that you necessarily consider it harmless. The question is whether you think that legalising it would in the end cause less harm than keeping it illegal. And for that, research from other countries that have begun the decriminalisation process, and from experiences with legalisin/banning other substances, should be the deciding factor.

I know canabis can be dangerous - it is linked with increases in mental ill health such as depression and psychosis, as well as with lung cancer. But I still think that it is illegal causes more problems - mainly that it is far more likely to lead onto harder more addictive drugs because that is what the dealer makes more money out of. If you didnt have to come into contact with these dealers, you would be less likely to end up on "the slippery slope". Given that so many people already use, or have used, canabis, I consider it unlikely that decriminalisation would lead to a large increase in people using it.