As I understand it, it's actually worse: the thing you swear under penalty of perjury is not "this content infringes a copyright", but rather "I am the copyrigh

As I understand it, it's actually worse: the thing you swear under penalty of perjury is not "this content infringes a copyright", but rather "I am the copyright holder or authorized to act on the copyright holder's behalf". So even if you know beyond doubt something doesn't infringe, you're not committing perjury unless you misrepresent yourself as a copyright holder or authorized agent of a copyright holder.