Part of the problem with McCarthy's explanation is that it presumes kiddie porn just miraculously appeared on a defendant's computer. It doesn't.
I've seen a few cases where a file or two may be brought in with the adult porn sought out by the defendant, but in each of those, efforts were promptly made to delete the files AND empty the trash from the computer hard drive.
Where there were enough images to get the attention of prosecutors, the defendant generally sought it out. The search terms are horrendous and the individuals KNOW what they are getting, even if they claim it was only 'age play' or some other thinking error used to justify their role in the harming of some potentially unidentified minor who is definitely a victim.
And federal prosecution is not something associated with the 18yo sending prick pics to his 16yo sexual partner (or vice versa). I know of a few cases where HS kids got wrapped up in STATE prosecutions but only after the pictures allowed their parents to know they were gay. There is a reason that certain pics between HS students are no longer felonies.
It is disingenuous to claim kiddie porn is a victimless crime.
Most recently, I had an inquiry from a Harris County case where mid-30's guy is found with multiple images. Kim Ogg's office gave him a deferred in late 2019. Less than a year later, the Motion to Adjudicate cites a new felony for failure to register because he did not list all of his online ID's, some of which were being used to obtain even MORE kiddie porn. He was also manipulating his behavior in polygraph testing to skew the results. Kim Ogg's staff and a Demonrat judge STILL allowed him to plea to one new count and a three year sentence while also dismissing the failure to register case. That is a pervert who IS going to get out and promptly re-offend almost immediately. That is ALSO not an isolated case. And if it happens at the State level, it happens at the federal level...