Well, no, you probably get all sort of arguments on what is or is not a "societal norm," especially with the effort these days to segregate and differentiate races and ethnicities and "cultures." "Societal norms" would be all over the map. There is no doubt that there are behind-the-scenes, as well as overt, deals going on to make certain laws. It happens all of the time. It doesn't necessarily make the law bad law. Laws, rules, and regulations are absolutely necessary. People just get pissed when one of them limits something that the person thinks shouldn't be limited.
For the sake of argument, assume that legalizing weed would be an overall negative for society, which isn't an unreasonable position. We should legalize something, even if an overall negative, because there is something else that was legalized which is an overall negative? Let's make society worse because this certain segment of the population can't legally openly (allegedly) engage in that activity? Of course you can make an argument that something shouldn't be legalized IF that something isn't a good thing. The whataboutism doesn't make the subject matter less harmful.