If I allow someone to get drunk in my house, or place of business, am I not responsible for the actions of that individual after they leave?  So, in these safe injection sites the user will simply get 'high' and return to the bushes or go somewhere to get more drugs.  Its more than likely they will resort to criminal activity to get them. How much responsibility will the Injection sites take  for that?   Assuming they were going to get high anyway is not a very good excuse. I don't think.
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 Why not just have some 'volunteers' donate their own homes and time to  take in as many people to snort, inject and...smoke?   Wait a minute, indoor smoking is also prohibited by state law where an employee may work.  How's that going to work and what about minors? Will they be checking ID?