Well technically it isn't black and white as criminal law doesn't always have an absolute either/or statement. So in some cases state of mind is factored in, whether it be mental health or otherwise.
Other than that you're absolutely correct, as a liberal do-gooder myself it is my aim to keep dangerous criminals on the streets irrespective of costs to society. That's exactly why I chose liberalism. I may well hide behind a thin facade of thinking that criminalising drug use and addiction serves no purpose other than to lead to "technically" criminal activities and you've seen through the standard liberal defence that perhaps there are other deeper societal and in many cases mental health issues that drive people to drug addiction.
It's all a lie and you have expertly seen through my lies. Instead all I really want is that demonstrable (again, it's not bankers I hate the most or politicians, it's that stupid liberal bias reality sometimes has where it clearly shows things like the following statement if only people would use a bit of that old Google) very small proportion of drug users who chose that life and are dangerous to society to be free on the streets for my own sick amusement.
Sure, there is a massive and long standing issue with understanding, treatment and help for people with mental illnesses where effectively they are left to fend for themselves, unemployable and vulnerable. But that's just the do-gooder in me and like the new iPhone, it doesn't take much to scratch off that do-gooder routine to get to the real truth (by which I mean an extreme inhumane view that has no basis in any reality or study ever performed).