Apparently I'm the only one who thinks it is, so I'll volunteer that I found it funny because it's unexpected and shocking, yet almost plausible enough to be be

Apparently I'm the only one who thinks it is, so I'll volunteer that I found it funny because it's unexpected and shocking, yet almost plausible enough to be believed, given Linus Torvalds' track record as a sometime verbal abuser of adults. Speaking of which, I just realized it also includes an unintentional satirical subtext that highlights the difference between how Linus most likely treats children (probably not like this) and how he demonstrably has treated adults (exactly like this). Which isn't "funny" per se, but there's your explanation. Explanations are rarely funny either, nor do they generally result in suddenly getting the joke and laughing. But I suspect that wasn't your aim anyway.