We have said, many times in many places, that All The Tropes is intended to serve not only as a fan site but also as a writer's resource and an encyclopedia. And it's that "encyclopedia" part that lets us invoke Fair Use as a justification for using copyrighted images.
Adding to the wiki something that the editor knows is misinformation makes the "writer's resource" status less reliable and puts the "encyclopedia" status at risk.
We cannot run that risk of losing the legal right to display all of the thousands of copyrighted images that we have on our pages just because one person wants to post a writeup of a nonexistent work - especially when that person appears to have created a second account in order to do so.
EDIT: It is trivially easy to get a free wiki of your own, at Miraheze, Wikia, or other sites. If you want to post descriptions of nonexistent works, I suggest you create your own wiki as a place to do that.