You can't blame a million middle managers. If all middle managers are doing something wrong, that's a problem of org design.
The same is true across the board. One corrupt congressman? Bad apple. 100 of them in a government? Something is wrong with the way the system is set up. One bad teacher? Bad apple. Most teachers are bad? You're looking at some issue with hiring practices, training, salary, incentives, management, accountability, transparency, administration, or something else.
These problems get hard to solve when blame is misplaced. You can't fix an org structure if you can't talk about teachers doing bad things since people confound that with bad teachers. The exact same person can be the most and the least competent based on the situation they're in.