If Walker's father pulled a Wenner (Jan Wenner, publisher of Rolling Stone and the father of a 10 year old boy at the time, left his wife to come out as a gay man), it has relevance to the case. Heterosexual sons of gay men go through hell, an identity crisis that makes typical teenage angst pale in comparison. They very often channel their anger into extreme behaviors, for example Taliban-like ascetism/militarism, as any therapist will attest.
It may not legitimately serve to mitigate his guilt for traitorous acts committed, nor should it spare him a stiff prison sentence, but it goes a long way to explaining who John Walker is, and it tells us far more about him than we can learn from reading The Autobiography of Malcolm X.