In the '70's urban paranoia had reached such a height, that the old white hatted heroes were no longer seen as relevant. And Hollywood answered with a new breed of movie cop, the kind that trampled all over criminal's rights as well as their spines.
These were heroes who were barely one step removed from their enemies, but as borderline psychotic fascist Dirty Harry and bigoted asshole Popeye Doyle rampaged through the streets, cleaning up the scum, we loved 'em. And they directly inspired every single action hero since, with the attraction that the viewer was at least vaguely challenged into whether these were the kind of screen heroes we wanted, or deserved.
Mad meanwhile, wasn't interested in all this socio-political nonsense. Here's Dirty Larry and What's The Connection?