If Bearsox felt that way, that would mean his viewpoint on pot would completely change if it was legalized. I highly doubt many people who call pot a gateway drug would be willing to change their mind if it was legal. Do you honestly think they would just wake up the next morning and say "Coke is the gateway drug of choice!" The argument is: Pot shouldn't be made legal because it is a gateway drug. Subbing in your definition: Pot shouldn't be made legal because it is an illegal drug.
Not everything that is illegal is completely harmful, and everything that is legal isn't safe. I think we as human adult should be able to decide for ourselves, with proper knowledge (school education, FDA, EPA, etc..) to decide what we want to do with ourselves provided we do not directly harm others with our decisions.