But you're not uploading something that hasn't been, you're mirroring something that's already up.
If you doubt me, see all verdicts for infringement when bitorrenting.
You have no guarantees that the content put up via IPFS is by the original copyright owner.
Thus immediately after you receive the infringing content over IPFS and start seeding it, you are infringing on the copyright owners rights. You have no recourse and no legal defenses to protect you.