I believe the theory is based on the idea that our language’s pronouns’ inate structure limits our ability the see or think beyond an individual’s sex—ie. as soon as we say ‘she’ we are referring to a female. This of course, explains the vile treatment women receive in English-speaking countries like the U.S.
The problem with this theory is that compared to most languages, English has very few gender markers. There is an Indo-European language that does feature gender-free pronouns—Persian or Farsi and we all know how well women are treated in Iran and Afghanistan.
Or Chinese which is extremely gender neutral yet it’s a very male centric society.
PC is first and foremost a fight against reality.