And so we end up being governed by people who have no political ideas or personal ethics apart from those of the herd.
Maria Miller is a typical specimen. She fiddled because everyone else was fiddling, because the herd regarded such behaviour as a perk of the job. She might have got away with it if she hadn't been so arrogant- or if she'd occupied a place a little higher up in the hierarchy.
She's not exceptionally wicked. The problem is systemic.