She is going through this very dramatic split-up with her husband. She loves her husband and he loves her, but still they must split up, and so she has this talk with Edith. Her mother then explains that she is angry with her husband, Edith's father, not because he is gay - that is not the issue. Rather, the issue is one of fidelity, and that is why she is angry. At the same time, it is heartbreaking, because there is no specific cure or remedy.
Nobody is right or wrong.
There is no moral agenda. Well, Joe comes to that realization, that everybody is by himself and that people die and of course the book is addressing a number of existential issues. Yeah, you have what you have and what you do with it before your time runs out. That particular passage is a dark passage and Joe is going through a particularly dark time. I also think there may be another answer, though, and that comes through the voice of Jenna, when she is talking to her neighor, Bill.