I would recommend at least on the legal side of things looking into the Duty of Care history, it's not necessarily intuitive though I think it makes sense in the end. As another person said, oftentimes it comes down to intent (though negligence can play a role in the matter as I personally understand).

Nightshade is intended to make minimal changes so I think that might be one argument though a difficult sell to some.

The original post is mainly about the current legality, I'm torn as to what the moral balance is, but poisoning data is similar to a lot of historical asymmetrical methods of topical influence through intentional property destruction, and that's an issue.

For example, the counterintuitive example of you poisoning a sandwich if your coworker is eating it makes you liable even if the original action is wrong on the coworker's part, if that makes sense.

It's not necessarily an intuitive legal construct but a necessary one at least.

That said, I think w.r.t. a final solution, grassroots vs big money legal will be the long-term playing field and I think efforts would be well spent on that. Though I worry about the perceived desperation of the field if people are this ready to poison open-field data in order to protect what they determine their own interests to be.

I think that's the big marker here that we should look at and be worried about, usually when ignored that tends to preclude different types of issues/problems.