Fair use is a defense. You can preemptively declare it as that, and hope that whoever you're parodying will see the light, but it doesn't give you immunity. Once a DMCA notice is served, and not obviously invalid, the content has to be taken down by the carrier. In exchange for having to do that, the carrier isn't liable. That is safe harbour. Simultaneously the content uploader can either get the supposed owner to retract their notice, or inform the carrier they'll hash it out in court. And only then, in front of a judge, does "fair use" come into play.