I thought I responded yesterday, but I don't see the posted comment. I apologized for not getting the thrust of your comment, I mistook the "druggies" in the first line to be generalized to everyone involved in the transactions.
In response to your second reply, there are a few scenarios I would probably look the other way, but it almost always be at a risk to myself. Allowing illegal trade to go on in your neighborhood is asking for trouble in many cases, especially for drugs. In the petunias scenario, I doubt anyone's going to get shot over getting wilted flowers, but when you don't have the force of law behind your transactions things get out of hand quickly. I saw and heard about lots of violence and theft when I dabbled in construction, when folks had to try and remedy disagreements themselves or get screwed out of money trading in illegal labor.
In the instances/scenarios I reference, there is nothing immoral about the objects themselves, but there's a reasonable risk that there will be blood when things go sideways and you can't go to the law to set things right.