Earlier quoted context omitted.
Roads are a public place, subject to constitutional reasonable regulation (by the states, not the federal government) as long as not in violation of our right to travel. So you picked a bad example. Case in point, if I own a vehicle that never leaves my ranch property it doesn't need license plates, insurance, or a drivers license to operate it, and I can go as fast as I damn well please. What I do in the privacy of…
If you think being told that people can't go above a certain speed on the highway to make highways safe enough to drive on makes you a "slave", I would tell you that you're being melodramatic. Civilization is a set of rules, either informal or formal, that we obey. We do this so we can live peaceful and comfortable lives. If you think that's slavery then I feel bad for you.
But once we step foot into your own property, I can take my guns anywhere I want. As long as I guarantee the bullets don't leave the property, I can shoot what I want. I can take any sort of vehicle I want at whatever speed I want. I'm the king of my castle and the land that surrounds it.
Now, as per drug usage - the bigger public health crisis is people ODing on the streets, urinating/defecating on the streets, needles exposed for people to get jabbed on the streets... Notice a trend here? "On the streets" is in public. Therefore public health crisis.
If I want to do drug, one of, in my own property, there should be no good reason for a government to say "You don't know your body well enough, so we have to tell you no". The result is a bunch of nanny-state politicians who want to dictate your body on your private land.
And, slippery slope? Well, tell that to NYC who can no longer sell larger than 12 oz sodas. Or other jurisdictions that enforce usage, rather than information. Nanny state at its best.
EDIT: So, what gives? Why is this "government knows best" idea so prevalent? The choice of how I treat my own body goes all the way to choosing to commit suicide. Most jurisdictions, even that is "illegal". Harming others directly - whole different story and that should have state "interference".