When I first started teaching literature survey courses in 1995 and I was required to use an anthology that was dominated by straight, white, male authors, I tended to assign more straight white male authors than non-straight non-white non-male authors. Sometimes a student would say, “I wish we could read more women” or “I wish we could read some Hispanic writers’ work,” but I don’t recall any student every saying, “There are too many straight white men on the syllabus.” The straight white man is the default setting.
The implication is that you can’t have “too many” straight white men on a syllabus, and that the non-staight non-white non-male authors should be in addition to the straight white male authors rather than instead of. My suspicion is that if Amy had lesbian writers in addition to the usual number of non-lesbian writers on the syllabus, there would have been no complaint (of course, then the students would rightly complain that there was too much on the syllabus).