The UN found that 90% of people worldwide hold bias against women. And because of the systemic nature of misogyny, it's not a far reach to say that the 10% that lies outside this statistic are prone (important keyword that you've seemed to gloss over) to those attitudes as well.
Prone means likely susceptible to or vulnerable to, not that they outright are what they're at risk of becoming.
Shutting down the moment you see "all" seems to me the clearest indication that a person has ceased any form of critical thinking or discernment. So at least you got one part right when you said that it's something you, first and foremost, would do well to remember.