Once is too much. Mind altering substances are taken for the purpose of affecting reality to one degree or another. Marijuana affects health as does tobacco and is as addictive as well. Marijuana also affects the mind more than users will admit. Don’t smoke is good advice for a healthy mind and body. Legal or not, don’t start.
More H.J. Anslinger/U.S. Gummint-generated horsesh*t from the 1930's. Absolutely, unequivocally wrong on both points. There are enough fact-based arguments against this God-created plant that one needn't spread concocted fallacies to weaken the otherwise arguable opposition.
;^)