Um...yes it should be legal. This topic seems very silly.
If you want to make a case that something should be illegal, that is a very high bar, and you have a heavy burden of proof.
I don't see how you could even make a case that marketing something should be illegal. There are many actively bad things in the world that should still be legal, imo, because the social cost to enforce a ban on them is worse than the social cost of letting people use them (drugs for example).