No, sexism in science doesn’t mean advisers take their students aside and say “don’t worry, you’ll pass your thesis defense, because I’ve noticed we both have a penis.” It doesn’t mean tenure committee meetings include the action item “DID YOU NOTICE SHE’S A WOMAN? INAPPROPRIATE? DISCUSS.” It doesn’t mean lab doors have signs saying “no open-toed shoes and no chicks.”
Here’s what male scientists and historically male-led departments do instead: Offer little or no maternity leave for graduate students. Evaluate women employees on their personalities rather than their competence. Make jokes that cause women colleagues to feel left out and belittled. Go on national television in a shirt that shows women as decorative, sexualized semi-nudes. Hire people who just seem to fit in with the culture that thinks all of this is okay.