Surely I can make the same claim about AIs. They wouldn't be particularly useful otherwise.
Well, a general AI with intelligence equal to or greater than that of a human without proven friendliness probably wouldn't be very useful because it would be so unsafe. See Eliezer's The Hidden Complexity of Wishes.
This is speculation, but far from blind speculation, considering we do have very strong evidence regarding our own adaptations to intuitively predict other humans, and an observably poor track record in intuitively predicting non-humalike optimization processes (example.)
...wouldn't be very useful because it would be so unsafe.
First, the existence of such an AI would imply that at least somebody thought it was useful enough to build.
Second, the safety is not a function of intelligence but a function of capabilities. Eliezer's genies are omnipotent and I don't see why a (pre-singularity) AI would be.
I am also doubtful about that "observably poor track record" -- which data are you relying on?
A stub on a point that's come up recently.
If I owned a paperclip factory, and casually told my foreman to improve efficiency while I'm away, and he planned a takeover of the country, aiming to devote its entire economy to paperclip manufacturing (apart from the armament factories he needed to invade neighbouring countries and steal their iron mines)... then I'd conclude that my foreman was an idiot (or being wilfully idiotic). He obviously had no idea what I meant. And if he misunderstood me so egregiously, he's certainly not a threat: he's unlikely to reason his way out of a paper bag, let alone to any position of power.
If I owned a paperclip factory, and casually programmed my superintelligent AI to improve efficiency while I'm away, and it planned a takeover of the country... then I can't conclude that the AI is an idiot. It is following its programming. Unlike a human that behaved the same way, it probably knows exactly what I meant to program in. It just doesn't care: it follows its programming, not its knowledge about what its programming is "meant" to be (unless we've successfully programmed in "do what I mean", which is basically the whole of the challenge). We can't therefore conclude that it's incompetent, unable to understand human reasoning, or likely to fail.
We can't reason by analogy with humans. When AIs behave like idiot savants with respect to their motivations, we can't deduce that they're idiots.