“what two consenting adults do in privacy” so, dopers and meth heads heroin addicts and coke snorters hang tight at home until they are safe to move among us on the highways, on machinery etc? What reality (altered) do you operate in?
If you actually read the post you replied to you would have your answer.
On the other hand, you have the moral argument, is it the government’s job to prevent us from committing crimes? Should the government outlaw alcohol because somebody might drive drunk? Fast cars because they might speed? Guns because they might use them in crimes?
The government has to give freedom to do stupid things and fuck up, and then punish if you do that. Once the government begins assuming you will do things wrong, and acts to pre-empt the wrong by stopping you from doing anything, even what you might do right, then you have problems.
If a druggie could do drugs, and stay home, I don’t think banning that is a good step for freedom, and it opens the door to a lot of other things.