I'm 30 and have been smoking half my life, so strictly personal I've seen many things that would make me think that it is something bad. Like a friend of mine going from being a extrovert prankster to evolving into a unrecognizable schizophrenic after he spent a year alone, smoking every day. Where I live "hash-psychosis" is a common term, and it is not something nice at all to experience it. Strictly personal I think it might be bad for the mental health, but I also think that some people, like cancer-patients, could benefit from it. But as a Christian I wouldn't say "nothing wrong" when I know that I myself and most other Christians would look at it as something bad. The bible tells us to not do anything that could make our brothers or sisters fall, so I would never offer cannabis to someone not already using it.