To me it is all very simple: I believe strongly that every individual has the God-given right to make all of his or her own choices in life - and deal with the consequences. This includes choices about what to eat or drink, whether to exercise or not, whether to go to college, whether to be into chicks or dudes, whether to drink alcohol, and yes, whether to use drugs. The logical extension of that is that no one has the right to forcefully interfere with anyone else making those choices. The Southern Baptists don't have to like the fact that I go out and have drinks with breakfast on Sunday morning instead of going to church, but it is morally wrong of them to try to use force to stop me. The greenies don't have to like my V-10 Excursion with the "drive a hybrid - I need your gas" sticker on the back window, but they have no right to take it from me. I don't have to like seeing two dudes kiss in public in front of my kids, but I have no right to try to physically stop them. This is the lens through which I view pretty much everything in life, and it's why I think drug laws are every bit as immoral and unjust as would be laws against homosexuality or violent video games or pornography or owning firearms or buying alcohol on Sunday.
Not only is it immoral to lock someone up because they choose to use drugs, but it's just horrible public policy. Prohibition never works. As a result, and quite predictably, the entire "war on drugs" has been an abject failure. It's done almost nothing to curb drug use in the US. Instead, it's cost billions of dollars, resulted in completely unnecessary police violence against countless non-violent people, and been the basis for a serious erosion of other civil rights over the past several decades. It feeds the violent black market for drugs that will never go away. The entire "war on drugs" has caused far more problems than it was ever even attempting to solve.
Drug users generally fall into one of two categories: the casual recreational user who lives a pretty normal life and isn't harming anyone else with their use, or the addict who seriously needs help, yet is probably still not harming anyone else with their use. It's a fact that very few drug users ever commit violent crimes, and it's also a fact that most people who experiment with drugs, even hard drugs, never become addicts. The stereotype of the person trying heroin once and instantly becoming hooked and turning to violence to feed their uncontrollable habit is a myth. In reality very few drug users fit that picture.
So this is why when I hear about someone being arrested just because they had some drugs on them, I don't assume they are some scumbag criminal who deserves to get beat up by the cops and then thrown in a cage for years. Quite the opposite, I see them as a victim of violence.