Well, political prisoners have been thrown into 'mental hospitals' and 'reeducation camps', and it's true that the history of mental illness is badly tangled up with politics and social hierarchies. Even today it's obvious that some 'mental illnesses' are perfectly normal reactions to horrendous circumstances.

That said, it isn't like it's some big conspiracy. That belief attributes power to the profession that it really doesn't have. I mean think about it: Most of the time these days it's hard to get mental health treatment even if you WANT it, so how efficient are these evil overlords anyhoo? Not very.

Still, there's a grain of truth to the political dimension of the DSM. It's just not as drastic as you are painting it IMO.