It's sexist because you assume male to be the default, just like the assumption that white is the default skin color is racist. The behavior outlined by the user above you follows from this thinking. Driving non-men away is a result of this behavior, which is the result of the sexist attitude that it's okay to assume everyone online (or on Lemmy) is a man.
The only people driven away by eir comment are misogynists.
It's sexist because you assume male to be the default, just like the assumption that white is the default skin color is racist. The behavior outlined by the user above you follows from this thinking. Driving non-men away is a result of this behavior, which is the result of the sexist attitude that it's okay to assume everyone online (or on Lemmy) is a man.
The only people driven away by eir comment are misogynists.