Dana White said he believes marijuana shouldn't be a banned substance. At least not on the same level of severity as steroids and other legitimate PED's.
Its the athletic commissions and government regulated aspect of MMA that decides what is a banned substance and what isn't. And what the penalty for testing positive is. That's what government regulation means.
Dana doesn't run the athletic commissions, its not his call what suspensions or penalties a positive test result merit.
Its funny how those who rant the loudest about others being uneducated and not understanding things are usually talking about themselves. I love irony!