I voted "Relative". In some cases, I think altering one's mind is fine. Other times I think it is immoral, self-destructive, and unwise.
I think the really "hard drugs" are immoral and stupid to use, and the same goes for abuse of some of the safer ones. I also think consumption of large amounts of processed food with their various synthetic or concentrated substances are very harmful.
For caffeine, alcohol, marijuana, peyote, and perhaps a few others, I don't think there is anything immoral about experimentation or mild use, assuming one is of age and the substance is legal in their region. They can have physical or mental consequences, but they can also have physical or mental benefits, including in some cases increased physical health, increased creativity, etc.
Carl Sagan stated that marijuana greatly improved his appreciation of art and music, and talked about major health benefits for patients with cancer or some other conditions. Steve Jobs credited prior use of LSD as a source of some of his inspiration. Aldous Huxley, author of Brave New World, went through legal experiments with Mescaline (active ingredient of Peyote) and LSD, and documented his experience in analytical essays.
Cultures back through prehistoric times have made diverse use of plant substances for mind-altering purposes, and in many cases the use was intertwined with their religion.
When my father was dying of cancer, both me and him wanted him to be able to use medical marijuana to improve his appetite and to improve his mood, but it was not legal in his state and therefore never done.
I don't think people should break the law, but I do think some of the laws about drugs in the United States and other places are irrational and harmful. I think some people have stances against certain drugs that are not supported by evidence, or are "black and white" thinking rather than recognizing the reality of the grayness in most things.
Personally, I consume some caffeine in the form of green tea on a regular basis, and I sometimes drink red wine with meals a couple of times per month. Green tea and red wine both have healthful effects with mild or moderate use, and I enjoy them.