The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
Elephant in the Living Room. If you know a certain work must contain the trope you're looking for, a good place to start searching is the page for said work (The Emperor's New Clothes in this case). This doesn't always work (no method is perfect), but most of the time, this approach is quite helpful.
Also overlaps with Abilene Paradox and The Dissenter Is Always Wrong.
Abilene Paradox comes closest to what I was thinking of, even though it isn't quite right. Thanks!
Everyone can see that something isn't true, but they all act like they believe it because everyone else says it's true, and they don't want to look stupid by being the dissenter.