Sexism is like racism. It's a pattern of behavior. It is difficult to determine that a single act is motivated by sexism unless the actor uses terminology that deliberately casts it in that light.

That's the way this stuff works, and why it's so hard to fight. Racism, sexism, homophobia, the list goes on. The reason is that bigotry isn't conscious, it's subconscious.

"No actual incidents"

Have you been living under a rock? There are more than enough examples.

Here's just a few examples documenting the sexism in science:

http://www.nature.com/news/gender-imbalance-in-science-journ... https://www.washingtonpost.com/news/speaking-of-science/wp/2...

Whoosh