If he wanted to sue, he really should have just gone for the consent angle and not the child porn one. Who exactly would agree that it's pornographic or exploitative? I doubt the vast majority of reasonable people would see the body of an infant in its natural form as anything but innocent on its own, but what do I know. They should have to demonstrate that the dollar bill makes people see the art as depicting child sex work; if this is requested somehow by the defendants,
the glove won't fit. This may be a missing detail, but he should have just asked the record company for some money before escalating it. If he did that and they refused, I'm sure that would have been a part of the news story.
The logical end to the argument is that children should never appear in any kind of commercial media because they can't consent, which... come on man. Worst of all, though I'm no lawyer, it seems like there's definitely a non-zero chance he'll get counter-sued by each defendant when his own lawsuit falls apart.