Some Google managers maintain personal blacklists
inc.com
inc.com
But now consider if you read a list created by various people, many of whom you've never met. The person you want to hire is on the list. You neither have the full feason the person is on the list nor the personal relationship with the perso who added the name to the list. Unlike in the previous cases, names can be added for no reason other than a personal vendetta or a political disagreement unrelated to work performance.
And that's why blacklists are far more than jist "not liking to work with some people". You can't know whether you like working with that person if you don't even know why theu're on the list or if the person who added them is lying.
From the worker's perspective, they get into an argument one day with a supervisor, get fired, and suddenly can't find work at any company they apply for. That's a chilling effect.
Or insert trait here_____ Woman Gay Right-wing Omnivore Muslim
Yikes! Actually terminated.
Grammar jokes aside.. they can't really choose to not protect the protected classes eh? But everyone has their blacklists, whitelists, etc. No rocket science.
Managers certainly should have influence on who is on their teams but obviously not absolute control.