Assuming there is no material misrepresentation of how this system operates, I would find it hard to argue that it is disproportionate to keep record of an IP address that somehow makes publicly available a file with copyrighted contents. I too would, from a pure self-interest perspective, like to share e.g. media with impunity, but for the sake of evaluating this opinion it's not reasonable to assume a position wher…
1) The data retention duration. France is holding some data sets for 13 years now without a charge forthcoming. I'm no expert on French law (or law in general) but it being a full-fledged liberal democracy with the rule-of-law, I guess there is some kind of a statute of limitation with regards to copyright infringement and I would find it hard to argue to keep the data beyond this point. Mind, the statute of limitations could be long-running (in Germany it usually is 30 years, unless the law says otherwise)
2) Seriousness of the crime. Under EU law data retention in the first place is only allowed in case of serious crimes. What is a serious crime? I think it arguable that copyright infringement is not a serious crime. To be not a serious crime it must fail to be a crime or to be serious. I think both positions can be argued, albeit being serious seems to be easier to unhinge.
But I'm not going to argue any of these ;)