if alcohol and tobacco had been discovered recently, they would certainly NOT be legal. They are so ingrained into Western culture that no party who proposed to ban them would get elected - unfair, but true.
Absolutely this.
I don't think all drugs should be legal, but I do think that that drug laws should be reviewed and rationalised based on science.
Legalising (some drugs) does not make it a free for all; I would assume that like alcohol, there would be a lot of restrictions around its manufacture, especially more dangerous ones (spirits) - you're not allowed to set up a distillery without a lot of paperwork. You can’t sell alcohol without a license. You can’t buy it if you're under 18. You can’t do things like drive if you've been drinking (not legally, at least; obviously it does happen.) Being drunk on duty would be gross misconduct in every job I've ever had.
If drug control laws were changed, I would expect them to be similarly controlled and restricted, and alcohol and tobacco should be part of it all. I'd be happier to consume drugs that I knew had been through some control process and that I knew the strength of, like you see on beer and cider and wine and spirits labels. It wouldn't eliminate under-age use (many of us will have sneaked a fag round the back of school and been drinking before we were 28.) It wouldn't eliminate crime (there's plenty of that around alcohol and tobacco still,) but there's already a lot of time and money spent on fighting drug-related crime (and smuggling of otherwise legal alcohol and tobacco,) but it would reduce it, and would generate tax income. It wouldn't eliminate all harms and addiction, but we already have a lot of support for addicts who want help, drugs and alcohol, and going back my alcoholic mother, if they don't want help, it won't matter how much is out there.
Lots of people go out at weekends and have a few drinks without becoming addicted; others wreck their own lives and those of other people. Same happens with illegal drugs. Legality doesn't change this. (Same with abortion, as someone said upthread. You don't stop them, you just stop them being safe and legal.)
I wouldn't expect every drug to be legalised. I would expect some to be strictly controlled within medical settings, as is currently the case - opiates have always been massive important in pain management, for example. It's ridiculous that medical research into drugs like cannabis wasn't allowed for so long. And decisions around legality should be based on actual research into known risks, not on whether it's a vote-winner or not, but no political party will go for that,because they want votes more.