Okay, that's just silly because it implies all prohibitions against substances and behavior are equally bad just because they are prohibited. Society prohibits certain substances and behavior because they are dangerous, both to the user and to society at large.
Straw man. I'm not arguing that all prohibitions are equally (in)valid. But, you seem incapable of distinguishing the harms of a drug from the harms of its prohibition, and there are plenty of on-topic examples from Prohibition, e.g. shooting law officers.
Murderers cause objective harm, depriving another of life, and therefore the costs of prohibiting that particular behavior are worth it. But this case is a lot harder to make for prohibiting suicide - or for doing drugs, which might just be a slow form of suicide. The other bad things that druggies do, e.g. theft, violent crime, are also and are independently illegal, and can remain so without influencing the discussion about whether the costs of drug prohibition are worth it. In fact, one of the costs of drug prohibition is that violent criminals are released from prison early, to make room for nonviolent drug criminals, with mandatory minimum sentences. I don't know about you, but I think that's simply disastrous policy.