Because tech companies have never followed any significant rules regarding employment, most tech companies are de facto hostile work environments, even if they

Because tech companies have never followed any significant rules regarding employment, most tech companies are de facto hostile work environments, even if they try not to, because of the behavior of individuals toward each other. There's a culture that is changing, if slowly, but this is basically always the case. IMO what it means is that people should work extra hard not to contribute to a hostile work environment, or expect to be perceived as contributing to a hostile work environment at randomly unpredictable points in their lifetime.