The point is that yes, there is PR involved. However, not having a toxic workplace is another. It is an idiotic suggestion that the perception of how good it is to work at one company or another is purely a matter of PR. Engineers talk to each other and do very frank "what it was like to work for BigCo X" all over the place. I think you probably understand this but it doesn't really fit well with your agenda here.
Honestly, work at a lot of companies is a drag, for a lot of people. Big deal. However, stories like the ones coming out of Uber are far outside the norm, even if you think that the endless publicity about shiny happy people working at same of the other companies is a product of PR.