A great move.
The major problem is addiction, but the vast majority of people would not become addicted just like drinking. People usually don't become alcoholics because they drink, it is more the need for something more. Some of the drugs are far more addictive to be sure, but people would generally not go down that road if they have things to be responsible for.
If people are worried about children being in a households with a crackhead, that is what protective services is for. The situation would be dangerous for them not because their parents are druggies, but because they would have been bad for them regardless of the situation.
And as far as stealing to get their fix, that is more a issue of income levels. Right now you don't see CEO cokeheads holding up people while wearing suits for some pocket money to get to their dealer. The drugs don't do this to people it is poverty.
If some 50 year old man lives alone works a shitty job, comes home to a dreary ass life wants to shoot up and then go back to work the next day for the rest of his life to escape how shitty his life is and get some kind of enjoyment, who are we to say they shouldnt have that right.
Now if someone becomes a criminal that would be different. If they cannot keep their shit together, that is what a forced rehab and prison is for, the crime, not for doing drugs.