In his latest missive, he justifies his views by claiming that drugs make people more likely to rob, cause car accidents, under-perform in work etc. So, what? Punish the robber for the act of robbery, punish the drugged up driver for the actual harm they have done and sack the lazy worker. In the first case, he is falling for the exact same bullshit that our tender-hearted judges do, every time a criminal plays the violin about how 'it was the drugs wot made me do it'. The day judges stop treating drug addiction as some kind of mitigation is the day criminals stop claiming addiction as the cause of their wrong-doing.
Hitchens' main error, in my eyes, is that he believes that the state should outlaw immorality. When he says that taking drugs is immoral, he has a point, but it is not for the state to rule on questions of morality, which will always be subjective. The only valid basis for declaring something a crime is that the act aggresses against another person or their property. Taking drugs does not do this. It may indeed harm the body, but that body belongs to the perpetrator. You cannot commit assault against yourself, any more than you can steal from yourself.
The state does not own me. It is none of the state's business what I do to myself. I do not need the state to protect me from myself, and I will not accept its claim to do so as a valid justification for violating my liberty and my property, so bring back some Victorian values and get rid of these ridiculous drug laws.