Typical authoritarian behavior
The benign nature of marijuana is pretty well established, both by clinical trial and by widespread and ubiquitous public use for almost half a century. The refusal of the authorities to recognize this and to continue to persecute users can only be explained as an attempt to save face by covering up a colossal mistake. The authorities simply have too much emotionally invested to admit they made such a gross error so they continue to devise new excuses why they should contine doing so. They simply don't want to admit they are wrong about this, or anything else, for that matter.