Of course most people know - or should know by now - that cannabis [the Evil Weed, Marijuana!] doesn't kill anybody. It is not carcinogenic and appears to be an untapped source of new medicines.
For those who ARE behind on their information about cannabis I point you to this pdf Congressional Research report on Medical Marijuana:Review and Analysis of Federal and State Policies
This is a special report produced for the US Congress on your tax dollar. This report is made available to all your legislators and this represents the information available to them. It is a little over 50 pages in length and is focused on medical marijuana policy, but the real value is in the details of the report which clearly show that cannabis is not remotely the health hazard or social disruption tobacco or alcohol - or other hard drugs - are.
If you read this report you will pretty much know what you need to know in order to talk about the topic of "marijuana" like a knowledgeable person and not sound like the clueless people who just regurgitate US Government propaganda.
There is a review of the history of cannabis prohibition, and an overview of actions taken to ease or end this extremely backwards situation. Tobacco and alcohol kill millions each year: cannabis kills nobody. Yet it is still severely illegal most places. Even in states like California, which has pioneered the end of cannabis prohibition, the US Federal government and numerous right-leaning private organization maintain an endless blitz of false information and scaremongering about the issue whilst the US DEA continues to raid medical marijuana growers and 'dispensaries' for lack of a better term for the places where folks can obtain legal medical cannabis.