I guess I would agree that a photographer needs to be careful about using strange children as subjects, however, I would be more worried about a punch in the nose from a paranoid parent than a prosecution. Prosecutors in the US have an enormous amount of discretion and there will always be the odd one that makes odd decisions but ones I have dealt with make logical decisions.. I have worked child porn cases back when I was in the detective bureau and spent days with the prosecuting attorney dividing photos between "child erotica" (legal) and "child pornography (illegal)." Based on my experience, it would have been impossible for any of the illegal photographs or videos to have been innocently taken. To clarify: a toddler in a bathtub or a little kid walking naked on the beach would not have even been child erotica.
Again, I am not advocating abandoning caution nor am I denying that some small (<1%) of cases could appear before the perfect storm of both a prosecutor and judge who both lacked common sense. I am saying that taking a picture of your 1 year old in the bath tub is very very unlikely to result in law enforcement showing up at your door with a search warrant. Basically I would say "Be careful, but don't let being careful let you miss capturing important moments."
I think you are spot on with your comments.
Been a couple of stupid cases over here of photos in the bath - thrown out of course, but the sticks for some time.
However the bit that is worse is the violence or threatened violence which comes from the low-brow parents who believe everything in the press. Having been on the receiving end I try and take extra care to not even touch the camera in the prescence of children.