One of the problems is that if you are promoting drugs then it is assumed that you use drugs, and will therefore be regarded as untrustworthy and unreliable by a large percentage of people.

Probably the best way of gathering information is to look at the situation in the Netherlands, find out what the negative and positive effects are in the country. There are few reasons to keep weed illegal and it makes sense to legalise it as it will reduce crime levels, but as with a lot of things, logic does not prevail. Governments and conservatives simply think "they're drugs, they must be bad. Because they are drugs."