Why not? Sharing your experience with working with people is fine, they're subjective opinions. Does this mean it's slander and/or a hit piece? Seemingly a lot of people would say so, personally I don't think people sharing those sort of experience publicly are doing so out of spite, some of us are just still used to the old-internet where you can share stuff like this in public, without getting piled on for not "thinking/writing the right way" or whatever people are complaining about.