There exists a lag between becoming a public nuisance and being dealt with, within which damage can be incurred by those experiencing the nuisance. The probability and severity of the damage dictates whether or not society decides to allow it.
As an uncontroversial example, maybe someone is well qualified to manipulate explosives in their garage. But society would still say the risk is not worth it, because by the time the “nuisance” is dealt with, there would be unacceptable losses.
The relevant measures to be discussed are what is the probability of someone using PCP and not being a nuisance, and if they did use PCP, what severity would the nuisance be?
Do you have any high-quality studies towards these relevant measures? Because your proposition is: "I think this man might be on PCP. He is otherwise doing nothing wrong. He should be imprisoned." That is ridiculous. A sober person is equally as capable of becoming a nuisance. So your actual proposition is to jail people on your presumptions, values, and opinions.
As an uncontroversial example, maybe someone is well qualified to manipulate explosives in their garage. But society would still say the risk is not worth it, because by the time the “nuisance” is dealt with, there would be unacceptable losses.
The relevant measures to be discussed are what is the probability of someone using PCP and not being a nuisance, and if they did use PCP, what severity would the nuisance be?