Classical liberalism is about freedom. Sure, It's about economic freedom first and foremost, But generally speaking it's about what will give the most people the most liberty. This is why Hayek's famous text, One of the foundational documents of modern classical liberalism, Is called The Constitution of Liberty. Now I'm not usually comfortable with banning stuff for no reason, And I don't think the government should ban things on a whim. But as a classical liberal I admit there's some things that need to be prohibited for the benefit of society, And drugs are one of them. They destroy lives, They can never be a victimless crime because the family and friends of the drug abuser suffer from it, They corrode societal values and they encourage crime and illicit drug dealing. The only freedom you get from it is the transient pleasure of getting high - something that usually leaves you addicted and enslaved, Not free. The freedom to take drugs really doesn't rank anywhere near important freedoms like the right to free speech and freedom of religious belief.
The short-term yes because most drugs give you a positive feeling and it is doubtful it can hurt anyone early in using it. In the long term no it does hurt people around you. It is really rare that no one has anyone around them. By you becoming addicted to a drug you are hurting a friend or significant other. It is not a victimless crime if it does affect the people around.
For the long term I think drug abuse should be punishable by law so that the person can find help in rehab and live like he did again pleasing the people that he affected when he/she was addicted.