So if a manager has a department composed of 100% of one gender they can't make sexist comments about their employees' clothes because there isn't someone of the opposite gender to see if it's 'sexist'?

It sounds a lot like things I've heard used as examples of sexism in lawsuits against companies before, so I'm willing to believe that it is sexist (sounds like it fits in my mind) and I believe it's what the writer was referring to in the title (whether others think it is sexism).