IMO it's not the drugs that are the problem for the most part, it's the users. Just like guns.
There's nothing wrong with Pot if you're responsible about it. There's nothing wrong with World of Warcraft if you're responsible about it. There's nothing wrong with sex if you're responsible about it.
Anything can be addictive, addictions can ruin lives, that's why people should be more responsible with things they could become addicted to.