That's really the core issue: too many people believe that they can evaluate a person's technical knowledge based on physical appearance, which ends up including gender, race/ethnicity, sometimes even religion (if the person is wearing religious attire).

It's just easier to get to know people instead of assuming.

Also: environments that are unpleasant/hostile/uncomfortable for "people outside the norm" make it difficult for such people to distinguish between sexism/racism/discrimination and legitimate feedback.

For example, playing with one's hair during a presentation is often a sign of nervousness, but it is also a signal that conveys that nervousness to the audience. Is it distracting to some degree? Maybe, but more importantly, it detracts from her authority. Still, I can see why she responded as she did--if you are constantly undermined, under fire or criticized for no good reason, it becomes difficult to filter out which criticism/feedback is actually useful.

Edited to add: Loved the artwork in that article.