@jonny True. They only notice it because it's different from their expectation, something they take for granted and "obvious" so it becomes a big deal for them.
Also, gender is a complex topic. Humans are complicated, which is what makes us fascinating to study. Fascism and libertarianism attract simple-minded people who want everything to be yes, no, 1, 0, black, white. No thinking required. Gray areas are to be avoided at all cost because they require thinking, making decisions, and taking responsibility. These are very uncomfortable things for about half the population.