Personally I don't know why sports sanctioning bodies even test for MJ. I see the point of testing for performance enhancing drugs and drugs which, while not created for that purpose, could enhance performance on the field (e.g., cocaine). Marijuana is not going to make any athlete faster, stronger, or more likely to quickly and effectively learn a playbook. To the extent it has any effect on athleticism (and any such effect is minimal), it is a negative effect. Really, who gives a shit?
Now, all of that being said, I find it hard to understand elite athletes who, like the HB, know full well that smoking weed could have a catastrophic effect on their careers, and do it anyway. That suggests a lack of discipline which would concern me somewhat if I were a coach or team manager.