That, to me, is where the rubber meets the road. When drug users become non or low functioning I now have to take care of them because of their poor decision, either indirectly via taxes and social programs, or directly if it be a family member .
As a citizen I could not just let them die in the gutter and I think that most here could also not do this.
So how is it the government's job to do what Christ instructs, to be charitable? If government was out of the way, you wouldn't have to pay for the folks who wantonly destroy themselves. With the concept of nationally required health insurance, you are forced to "take care of them," ultimately creating a breeding ground for immorality.
Even the Founders didn't write law banning our outlawing gambling, prostitution, drunkeness, and certainly nothing regarding charity. The Founders were wise -- they knew that the Christian bible provided the best municipal and moral code, as one of the Founders said (I forget which). Charity is the church's job, it is morality's job. The Government has zero to do with it, so you have zero to do with potheads or alchoholics who become society's burdens.
Anyone who wants to make sure potheads and alcoholics don't become a burden to them, should be clamoring for limited government, where people have the freedom to live morally.
I've learned over time that there's no "fixing" someone who isn't going to take charge of their own repairs.