I support decriminalization of mushrooms, but I think your question is somewhat irrelevant. When considering a new law, the thing people discuss is, "Will this have terrible side effects?" rather than, "Will this have worse side effects than alcohol?"
There are side effects from the status quo, too. Having a regulated safe source of product is better than allowing amateur mycologists to go out in the field and poison themselves as they do now. It doesn't matter what the law says, people who want to do drugs will find and do drugs, so we might as well make it a little safer.