They need to fix this and give us a detailed explanation, but assuming the de-listings are reversed then that glitch theory doesn't sound that far-fetched to me.
A person claiming to be a former Amazon employee commented on
this cnet article saying that he (or she) had once made a programming error that similarly seemed to unfairly affect a group of books. The first customer service responses about adult material were probably correct - according to that supposed employee, the search results would be swamped with adult titles unless Amazon made an effort to control that. So maybe some kind of bug really did cause a lot of works with certain tags to be unfairly ranked as adult books.
Ordinarily, I'd tend to dismiss someone saying they were an insider as a fake post, especially because they conveniently avoid details by mentioning a non-disclosure agreement. But it's tough for me to believe that Amazon has suddenly implemented seriously homophobic policies. Their company's nondiscrimination policy includes sexual orientation. They offer medical and other benefits to same-sex partners of employees. They even have a GBLT employee group.
Here's their Human Rights Campaign rating.
I know that Amazon has done things to earn the mistrust and bad feelings that a lot of people here seem to feel towards them, and I'm glad that people have been voicing their displeasure over this issue to the company. But maybe we should hold off on the torches and pitchforks and account canceling, just until we see how they respond now that the holiday weekend is over. But their fairly gay-friendly corporate policies make me want to give them the benefit of the doubt for a couple of days at least.
Of course the way that they've bungled some other problems makes me worry that they're just going to reinstate the listings and announce that they fixed the problem, with no further apology or explanation. I really hope they don't do that.