Axl Rose does make a good point about the drug issue in Singapore not existing and essentially they have been so successful in creating a culture that literally fears breaking the law (to the point of going to jail for spitting on a sidewalk).
The other issues, we can look back far enough where Al Capone became successful in Chicago because Alcohol was illegal and this pushed for violent mafias to take advantage of the bootlegging and created a whole criminal industry, some will say that by legalizing alcohol, it reduced the mafia influence but you still see the effects of the various DUI's, alcohol related deaths, and the other issues that Alcohol has created. So while the mafias and cartels cease to exist, the issues from that drug continue to exist.
Now for the war on drugs, by legalizing Marijuana or other drugs, you may end up killing off the supply of that specific drug but then you have to take into account the issues that would be caused with those hard drugs legalized. I smoke cigars occasionally, and maybe once a year will drink 2 glasses of rum and that's about it, but there are serious considerations as well that by legalizing the drugs, then they will likely be regulated or taxed and that isn't going to end illegal distribution of the drugs.
Look at the pharmaceutical industry, the drugs are regulated and there is no shortage of illegal steroids floating around, Canadian pharmacies, and oxycodone or prozac floating around on the streets for $80.00 a pill.
As for my personal view on drugs, I think hemp makes a great material for clothing and rope but I honestly rather not take a position on this, but I see no benefit to legalizing drugs, unfortunately in the case of making drugs illegal as well, it's not necessarily done in an effort to keep people safe, but moreso for profit both from corrupt government and the cartels. The drug industry is a dirty industry and a lot of people have lost their lives due to the psychotic drug cartels. When the economy is so bad that the only way to save it is by running a meth lab out of your house, we know that this country is in deep [censored].