"No, the real genius of Cuties – its destructive, almost evil, genius, unfortunately – is that it powerfully presents a narrative in which children’s sexual expression seems inevitably connected with seriously bad behaviour. When kids are sexually active, we are invited to believe, it is a clear sign of going off the rails big-time, even when the activity is confined to the symbolic level, through dance."

Logical. Because the commandments for a woman subject of a patriarchal religion - "Do not kill. Do not whore. Do not steal.". They are at quite comparable level of seriousness. Someone who is desperate enough to breach one of these could as well breach the others.

"Does child sexuality really have to be like this, joined at the hip with ruthless criminality? Does raunchy dancing really turn girls into daughters of Satan so mean a mafia hit-man would be scared to mess with them?"

Not in itself. But as I just said - a girl who is not desperate enough to breach commandments may have sexual feelings and desires, but she will obey ban on acting on them.

"Zen Thinker, in a comment here, said “I don’t want to see a society overrun by a cheap and tacky form of sexuality.”"
"Is this contempt for ordinary people and popular culture fair? Where does good taste end and snobbishness begin? Perhaps they are the same thing. Good taste – in dress, manners, music, whatever – is defined by whatever the elite of any society likes and does. Snobbery is often the slavish imitation of elite tastes by those who are struggling to put their own lower-class origins behind them. The term would have no meaning in a more materially and socially equal society. There would be no “cheap and tacky” sexuality, just sexuality. There wouldn’t even be “expensive and tacky” sexuality, of the sort said to have characterised Jeffrey Epstein’s private Caribbean island.

But we are where we are. We cannot realistically argue that we can only have good sex once we have established socialism, or gone back to nature, to the hunter-gatherer lifestyle that shaped our evolution and to which our bodies and temperaments may still be best suited."

In a certain sense, we can.
Because of your argument:
"What we can usefully do, though, I suggest, is to re-cast the terms of our unease over Cuties more accurately. What we have here is not a moral concern with tackiness but an aesthetic one, which ultimately derives from the nature of sexuality itself, which in its basics is not a matter of great refinement."

Here, I think, it is connected to the moral side.
"Bad taste" sexuality may include "whoring" - a female who is desperate for the benefits for sexuality other than her own sexuality, and who is willing to agree to sex she does not enjoy, OR to deceive her partner to extract benefits from him.
"Good taste" sexuality may include sexuality of someone who is NOT desperate to get nonsexual benefits out of other people´s sexuality - someone who can afford to say no, refrain from deceiving her partner and signal her ability to say no.
And then "snobbish" sexuality may be trying to be "poor but honest" doing honest work, desisting from theft and fraud, getting nonsexual benefits from a single partner who gets her honest services.