Folks made the exact same arguments about alcohol and marijuana. Specifically with alcohol, anyone can walk into a treatment center without fear that they'll be arrested for the mere _use_ of a substance. (Marijuana has very low risk and rates of addiction, physical or psychological.)
If "hard" drugs are legalized, then they will likely be treated the same as alcohol and pot and tobacco: highly regulated, sold only to adults in very limited stores, and folks can enter treatment without fear of arrest.
The big mistake California (and other Leftist faux-topias) made was decriminalizing THEFT, ASSAULT, smoking and shooting on BART, smoking and shooting in public parks, smoking and shooting on sidewalks in front of residences -- and taxing the legal pot industry so highly that it was miles cheaper to buy stuff illegally no the corner.