To clarify, well over 50% of the US population has taken pot at least once. Like alcohol many people don't appear to be negatively impacted by it. But, we don't hear "Please smoke pot responsibly" instead pot and people with an alcohol problem are demonized. People see anecdotal evidence and such as the large number of entertainers that admit smoking pot and assume it's safe. They then extrapolate to the sample size of their friends when evaluating other drugs. Ecstasy does horrible things to the human brain over time, but people don't evaluate the long term medical effects they just assume they are invincible and "the man" is full of crap.
I am further suggesting that for drugs that need a large scale distribution chain, and are extremely addictive and dangerous a more effective deterrent than prison should be employed.