In principal I agree with you. However, when it hurts someone else that is a different matter altogether.
I agree: don’t drive drunk or stoned, don’t go on public assistance to subsidize your substance abuse. As to prositution, as long as they don’t do it in the road and frighten the horses... I believe that in Nevada prostitution, like gambling, is legal but confined to locales where it does not constitute a nuisance. Most of the ills associated with drug abuse are exacerbated by prohibition.