You wrote:
“Where did you ever get the idea that “conservatism” necessarily means that one must be opposed to the use of one or more substances for purposes of pleasure?”
That would not be use, but abuse. A substance that is used to get stoned - and is essentially ONLY used to get stoned - would not fit into the general conservative belief in personal responsibility very well.
“That is merely an accident of history. By that notion you would have to argue that the only true conservatives are Mormons.”
No. Again, we are talking about the abuse of a thing, not the use in itself. There may be purposeful uses for marijuana that make sense, but getting stoned would be a violation of personal responsibility. Remember, Jews, Christians, Muslims, none are supposed to get drunk, intoxicated, and yet that is essentially the goal in the use of pot. It seems to me that you can not separate the monotheistic concern for personal responsibility that is at the core of conservatism’s belief in freedom while pushing for the use of an intoxicant for the sole purpose of intoxification.
And in the end, it seems to me that “conservatives” who make arguments in favor of drug use just want to get stoned without it bothering their conscience. I doubt that there were too many conservatives who would have made such an argument before the rise of the leftist radical drug culture 50 years ago. Apparently many so-called conservatives have been tainted by that leftism and mistakenly believe they are standing up for a “freedom” which has no place in conservatism.