"Women weren't the intended audience" is an excuse for sexist incidents in which the excuse is that women shouldn't have been/weren't expected to be listening or taking part in the place where the incident took place.
This excuse seems to place sexism as something that is a sort of etiquette problem, in that it shouldn't take place in mixed company. It ignores the fact that many men are anti-sexist, and that creating a sexist environment signals that it is likely to be oppressive in general (for example, an environment that is anti-women might be reasonably supposed by gay men to be homophobic).
This is related to Invisibility, except rather than pretending that women aren't present or being surprised that they are present, it tries to insist that they not be present (or not listen).
