What if I told you that PI contains child porn?
As there are a lot of people who are quite opposed to Bitcoin/PoW/blockchain/etc, I assume if it was true, someone would have come up with some indisputable, solid evidence for it, and it would make the tech news rounds for quite some time (there are enough anti-Bitcoin writers and commenters that such a thing would never die, and would be brought up with some links to the evidence in literally every article written about Bitcoin).
As that's not happened, I remain inclined to treat it as rumors and "But if you use this OTP you can get the following out!" sort of trickery.
There are JPGs, ASCII art, PDFs, religious messages, firmware keys, "illegal" prime numbers and all sorts.
Is there anything worse than that? There are certainly some GPG encoded files in there. Perhaps someone is planning on shorting Bitcoin and is waiting to announce something so evil is stored that possession of the chain becomes a criminal offence is most countries.
However, the specific claim of CP remains, as far as I'm aware, entirely hypothetical. And I'm at least not aware of any legal precedent that says the possession of random data, of which you don't have the keys, and don't have any reason to know the content of it, is illegal.
I found this reference for you: https://fc18.ifca.ai/preproceedings/6.pdf
See under "Illegal and Condemned Content":
> Bitcoin’s blockchain contains at least eight files with sexual content. While five files only show, describe, or link to mildly pornographic content, we consider the remaining three instances objectionable for almost all jurisdictions: Two of them are backups of link lists to child pornography, containing 274 links to websites, 142 of which refer to Tor hidden services. The remaining instance is an image depicting mild nudity of a young woman. In an online forum this image is claimed to show child pornography, albeit this claim cannot be verified (due to ethical concerns we refrain from providing a citation)."
I'm sure if you really put your mind to it, you could find and recover the images, but then you'd just have illegal content and that's not very useful, so why dig for it?