If we want to make a drug illegal it should be alcohol anyway. It causes huge numbers of deaths every year. It’s probably the most dangerous drug we have.
Clarification: All I m trying to say is that it's dangerous to say "there is no addiction risk in mushrooms. They are totally benign". If you say that it will be really easy for opponents to find counterexamples. Instead we should say they are not more dangerous than already legal things so there is no point in prohibiting mushrooms while other similarly harmful things are legal.