Promoting a sexual performance by a child is a sex crime, and as
defined
generally includes the promotion of lewd exhibitionism.
Well, yes, but then it comes down to what you consider to be lewd.
No, it comes down to what is the proper definition of lewd within the context of such a law.
Ok, so it comes down to what a reasonable person considers to be lewd. (At least in the UK, there is no set definition of "indecent", it's up to a jury.)
That's not what I said, although I don't understand the distinction you're trying to make.
What's not what you said? And what distinction? I'm trying to make the point that there is no obvious definition of lewdness and plenty of people don't consider the Virgin Killer picture to be lewd (highly distasteful for an album cover, sure, not not lewd), seemly including the UK police (and the US police, although I don't know if that version of the cover is still on sale in the US so it just be a matter of times changing and were it released now the police would act).