There are lots of salient differences between tobacco and psychedelic mushrooms, but they are mostly of the "banning tobacco would be much more reasonable" variety. I think that was the point.

Only if you ignore cultural path dependency which has a huge impact on the utility and adverse consequences of a ban.

Laws can only be meaningfully evaluated in a concrete social context.

So what if it's only purpose is to get high?

What moral high ground do you have to say others can't get high?

Some people just know that they're right. That they have "the truth". Burroughs called it the "Right Virus". That was before we had the concept of memes.