Kids at that age pick up some weird shit from their classmates. Just correct his misconception. It’s not likely a belief he came up with on his own, he’s just parroting something his best friend said.
And maybe a light tap upside the head, for emphasis. =)
I would conjecture that it is just an epithet he has heard and has no more idea what it means than, say, fuck. He may associate it with Sandusky, but when I was nine, I had no idea of sex of any kind. But I certainly knew the word “fuck”.
Hell, I had sex ed in school at 10, and still didn’t know diddly after that. I understand giving it early, but why not continue it up to and through the point where you can actually USE it? By the time I needed it, I didn’t remember shit. Not that it mattered, it wasn’t as if they were teaching anything USEFUL. 
Well, it’d be off-message for them to use straight sex for their rape-of-choice, now wouldn’t it?
He’s just parroting something somebody said. When my son was about that age we asked him if he knew what “gay” meant. He said it’s “boys humping boys.” Good enough for the time being I guess, except I wanted to know what he though “humping” meant. That he wasn’t so sure about.
Jeez, that’s horrible – it’s like 35, 40% at best.
–Cliffy
I’m with Sattua, but at the same time 9 year olds think anything about sex is icky, doubly so if it’s to do with a relationship they can’t have the slightest beginning of an inkling of empathy for (assuming they’re straight).
My daughter’s 9, and she knows all about my straight-but-not-narrow beliefs; we had a “Vote No on Amendment One” yard sign, and I told them what that was all about, how gay people have equal rights, etc.
A while ago we had this conversation:
Her: “I do think that two men or two women should be able to get married and everything, but I still think it’s kind of disgusting.”
Me: “Well, as long as you recognize their rights, it’s OK not to like someone’s behavior or beliefs. But to be fair, you probably think straight sex is disgusting too.”
Her: Emphatic, wide-eyed nod
I agree with this.
Plus, most of what’s going through the kids head is pure abstract nonsense, and what comes out of his mouth is likely uncensored bravado. Give him a nudge on this one but don’t be too surprised to hear more nonsense in the years to come. He’s just howling at the moon.
At the age of 9, I doubt I knew what the words “gay”, “homosexual”, or “rape” meant.
He’s 9 and he knows about rape? At what age was he first introduced to the concept of plain old intercourse?
That’s the cutest thing ever! 
You’ve got to walk before you can run.
I suspect most kids learn the swearing definition of the word ‘fuck’ before they learn the literal. Same with rape, I would imagine. I see/hear it in gamespeak fairly regularly.
They can run? FAR too old.