By your logic, unhealthy food should be illegal, and the fact that alcohol is legal is an abomination. Along with motorized vehicles, base jumping, fireworks, and swimming pools. And I'd still like to see any reasonable logic that suggests drug-related accidents would increase. I'm sure numbers from during and pre- and post-Prohibition have been quoted in this thread already. You should read them.
The Constitution is clear - the government is here to protect our freedoms, not be a babysitter and tell us that we can't do things that might hurt us. You also seem to be suggesting that it is okay for the government to tell us what we are and are not allowed to do even when there are no consequences on others.
Where do you suggest drawing the line? Because right now, your case is COMPLETELY untenable.