I think it matters when some of the fighters that get caught have a medical exemption to use it. You can use TRT with a doctors note, why should marijuana be different?
I have no problem if it is medical marijuana and I believe NSAC has already previously stated they would allow it. The problem with the Diaz case(which I am guessing you are referring to) is that Diaz was an idiot and he didn't make it known that he was taking medical marijuana. His case is no different then other fighters that have failed to disclose pain killers/steroids etc that they were taking for health reasons