You can't stop people from using even the most devastating drugs simply by making drugs illegal to produce and distribute. There will always be someone willing to take the risk, regardless of the penalties. Criminalization is the WORST form of regulation. Instead of ending up with a dangerous, yet pure product, from a trusted, regulated supplier, you end up with an impure and potentially deadly product from an unregulated and completely untrusted supplier.
You can judge drug users all day long, but they're going to seek these drugs regardless of the prohibitions. And there will always be a criminal willing to supply the addiction, because the demand is 100% inelastic (i.e. totally unrelated to price).
Drug criminalization has created a $400B global market that fuels terrorism, human trafficking, child exploitation, and the destruction of democracy in many corners of the world.