WHAT if it had been a 10-year-old girl in the Penn State locker room that Friday night in 2002?

The likely answer to that question reveals an ugly truth, one that goes stubbornly undiscussed. Whichever version of Mike McQueary’s story you choose to believe — his grand jury testimony, in which a “distraught” Mr. McQueary, then a graduate assistant to the football team, “left immediately” after witnessing the former assistant coach Jerry Sandusky sodomize a young boy, or the e-mail recently leaked to the press, in which he wrote, “I did stop it, not physically ... but made sure it was stopped when I left that locker room” — the mind recoils at the grotesque failure to intervene more forcefully. How could a grown man have left the scene without taking the child with him? Mr. McQueary wants us to imagine that his brain was racing during those “30 to 45 seconds,” that he “had to make tough impacting quick decisions.” But it seems clear he wasn’t thinking at all — and it’s hard not to wonder why.

I think it was the gender of the victim.

Does anyone believe that if a burly graduate student had walked in on a 58-year-old man raping a naked little girl in the shower, he would have left without calling the police and without trying to rescue the girl? But the victim in this case was a boy, and so Mr. McQueary left and called his dad (who didn’t seem to think that it was a matter for the police either).

Mr. McQueary’s reluctance to treat what he allegedly saw as a flagrant crime, his peculiar unwillingness to intervene “physically,” the narrative emphasis on his own trauma (“distraught”) rather than the boy’s, the impulse to keep matters secret rather than provide rescue, all suggest the presence of a particularly intense shame, one occasioned less by pedophilia than by something everyone involved apparently considered worse: homosexuality.