Most companies give managers the ability to be extortionists if they want to be. That doesn't mean that all managers go black hat. Many do not.
I've seen companies where 90% of the managers were decent people, and companies where zero percent were decent people. It seems to average about 70, but that bad 30 percent can do a lot of harm.
In my experience, managers are like programmers. Good managers can be really effective. Most are semi effective. Some are downright harmful. For the most part though companies seem to have limited ability to tell which is which. I went through a major re-org over year ago. Just from the management switch my stress level went down by a factor of 10.
I've seen companies where 90% of the managers were decent people, and companies where zero percent were decent people. It seems to average about 70, but that bad 30 percent can do a lot of harm.