Malicious Actors And Storing Data On Blockchain?

Let's say we have a 'malicious actor', someone who hates a particular cryptocurrency and wants to destroy it at any cost, regardless of ethics or legality. To explicitly state, this is purely hypothetical and thus I will be vague/general as I can, to convey the point rather than get hung up on specifics and nuances. Blockchain can carry and store data permanently, that much is established. What if someone were to take something inherently illegal to even own or view - we'll say for this argument it is the most morally and legally reprehensible pornography you can imagine (again, up to you what this is), since this can be mere kilobytes of information for an image, and unlike information/data does not ever become less relevant of a concern, whereas information can become no longer relevant or dangerous (especially once it gets out), and they write it to the blockchain? While it might be fairly expensive of course, we'll assume this person has infinite resources for arguments' sake. Would it then be illegal to own a whole copy of the blockchain, since it contains this morally and legally reprehensible content that could be reproduced by anyone with the whole chain, and impossible to get rid of? And if that would then make it impossible to legally own a whole copy of the chain, what's to stop someone from having done this already? And wouldn't that basically give law enforcement grounds to claim anyone with a copy of the blockchain has "illegal pornographic materials" and charge them accordingly?

I don't know a ton about crypto, I will be honest, but I was just thinking about the whole "immutable" thing and how that could probably be a concern. I'm also not the brightest bulb so I'd imagine this has already been thought of by someone, and there's probably some decent explanation of why it's a non-issue to offer that I don't have.