Let's not pretend that the laws against psychedelic use are there to protect the users.  Psychedelic use is a lot more dangerous due to prohibition because accurate information is not as readily available, quality, quantity and substance is harder to verify, and the violence resulting from the black market.  Psychedelics are readily available regardless of their legality or lack of, and anyone that wishes to do them will.  So the only thing being illegal does is create a more dangerous environment for the users and even non users, while usurping peoples fundamental rights to do with their bodies (and minds) as they wish.

A blatant disregard for personal safety is a persons RIGHT.  People exhibit this in many ways, some more socially acceptable and legal than others.  I have yet to meet someone that has used this as an excuse to make something illegal and be consistent with it. 

You can be concerned for others and offer them information that you believe they are in need of and/or may help them to act in a way that is less concerning to you, but you don't have the right to stop them.

It is a crime, and it still would be if psychedelics were legal.  If I go out and hurt people, if doesn't matter that I did it while I was drunk, stoned, on acid, or sober.  I am responsible for my actions and should be held as such.  If I chose to take those substances in a reckless manner and then hurt someone, it was still my actions, I am still responsible and it is still a crime.  The substances aren't to blame, and me being on them does not absolve me from my actions even if they are legal.