I think you're trying to make an argument for personal responsibility in recreational drug use. I'd agree with you, if you hadn't made the two unrelated examples which have led to you arguing in bad faith. (Thus undermining your entire point.)

That is, speeding and overdue fees are basically harm reduction actions in the form of sanctions against the person responsible. Both work at preventing people from placing others at risk of harm. (Collisions and preventing access to books, respectively.)

Now risk of harm in recreational drug use is another matter entirely. The sanctions and their effect have thus far worked something like this:

1. Sanctions in the form of preventing access to amphetamine precursors (Government of Canada managed) have not succeeded in reducing the harm to society from recreational drug use.

2. Sanctions in this form previously mentioned have increased it, as seen through the death of teenagers from ingesting what they thought to be MDMA, which was in fact a toxic knock-off.

3. Harm reduction actions such as safe injection sites for heroin users (Health Canada managed) and cool rooms/fluids for MDMA use at raves (community managed) have been shown to have a positive benefit on public health.

So really, we've got an issue here to discuss about the effects of prohibition as a means of harm reduction.

tldr; Don't argue in bad faith and create strawmen.