The only truly immoral action I can take is to judge another person. Each of us is living on a continuum between birth and death on the physical plain and between ignorance and enlightenment on the spiritual plain. Each of us is evolving and is responsible for their evolution.
Separating moral from legal is an important distinction. Where I may sit on a jury and judge whether something done was legal or illegal and whether the person may have to face consequences based on their action is totally different that morally judging anyone as being good or bad.
If I remember correctly it was once said, “He without sin cast the first stone.” Many of my friends have smoked and some continue to smoke marijuana and I choose to no longer participate. I believe it hinders creativity and brain function, particularly after long term use. Having said this I also know that some people choose to experiment. To judge and make them emotional outcasts does nothing for the evolution of humankind. When I allow my heart to stay open and welcoming they have a safe haven in which to come.
I want to be very clear that if someone came to me and wanted to my opinion about the use of drugs that I would certainly talk about the negative effects, from a place of a choice each of us make not moral condemnation.