While I generally have a positive view of digital piracy (digital archiving), this is ultimately going to happen to any social media site after it gets big enough, it should be seen as a good thing for Lemmy (growing pains). Either a site gets in trouble and/or shut down for opening itself up to piracy or it proactively bans piracy. Unless Lemmy gets full-time staff to actively moderate and keep an eye out for pirated content in a community dedicated to piracy. It probably couldn’t handle such controversial community that might bring the ire of the Entertainment Industrial Complex on them.
Digital Piracy will continue and we’ll likely see them spin up their own “Pirate Bay” instance somewhere else. Lemmy.world will almost certainly defederate from them, but they’ll be around to those that know where to look, just like pirated content in general.