Of course 'they' have found a way around it. Cannabis < the latest and greatest in MK tech, clearly.
'They' certainly want people consuming alcohol, industrially-produced cigarettes, heroin, cocaine, etc. over cannabis. But I would agree with you: why the legalization push from the usual suspects? Certainly suspect, clearly ulterior motives at work.
I'm sure it does interfere. But considering the realities of MK and the associated tech that we are aware of (V2K, etc. etc.), it would be naive to assume that just a plant alone could counteract them.