Do you think there would be fewer needles outside your apartment if we simply locked these people up? I think there would be more.
I agree that the limits of rehabilitation need to be seriously considered, and that good policy requires a mix of approaches. That said, all of your arguments could be applied to alcoholics during prohibition.
I think if we actually want a sense of community in this city, it starts by treating our neighbors as humans. These drug users are your neighbors. What are you doing to help them?