An all too common phenomenon among characters who bash things: they don't actually look at what they're bashing. These are the people who insult movies before they even come out, or claim a video game Rated M for Money has more deplorable content than is actually there.
Also, sometimes this can be invoked if some leave out the full context of complaints to make a show they don't like look bad. Sometimes character could complain about a part of a show, and it may actually be worse than the person thinks. Or they might end up disliking a show for a different reason.
Now there is some Truth in Television to this trope, but while some people have revealed (directly or accidentally) that they haven't watched shows, just as often many will accuse them of it simply for criticizing it (even when people are merely criticizing preview elements for shows not out yet).
Even for characters in a show doing this, this trope can be driven by other reaction tropes, such as:
A pretty audacious example appears in Gekkan Shoujo Nozaki-kun. Several gags imply Maeno, Nozaki's former supervising editor, nearly never reads Nozaki's scripts!
The Far Side: One comic titled "Hell's Video Store" featured a store run by devils with nothing but the movie Ishtar. Larson later apologized for drawing that strip after actually watching the movie Ishtar, which he had not seen it at the time he did the comic and had only used it because of its reputation. After seeing Larson admitted he found it funny.
"Suddenly a rocket WOOOSHED past and left a big line of smoke and a bang at the end where it missed but only the helicopter because it still hit another tower but it was okay because noone was in the tower except for that leloosh guy (MORE LIKE LELOSER AM I RIGHT!) an d everyone hates him so its cool except he has a giant robot and also ive never seen it."
Matinee: Citizens For Decent Entertainment protesting against Mant without having seen it. It is, of course, a stunt to drum up publicity.
Don Quixote: With Don Quixote: At Part II Chapter LIX, When Don Quixote hears someone talking how he is not more in love with Dulcinea del Toboso, he is full of wrath and indignation. So he read only a few pages of Avellaneda’s Fan Fiction about him. After a discussion of how this Continuation Fic is full of Character Derailment for Don Quixote and Sancho, Don Quixote believes that the book is bad and not worthy of his time or effort:
... though Don Juan wished Don Quixote to read more of the book to see what it was all about, he was not to be prevailed upon, saying that he treated it as read and pronounced it utterly silly; and, if by any chance it should come to its author's ears that he had it in his hand, he did not want him to flatter himself with the idea that he had read it; for our thoughts, and still more our eyes, should keep themselves aloof from what is obscene and filthy.
Lord Peter Wimsey: Harriet attends a literary party, where a gang of authors take turns theorising why some thoroughly arty and undeserving novel has been awarded a reviewer's prize - because of advertising deals, or political loyalties, or familial connections, or other underhand reasons. Naturally, none of them have actually read the book, or have the faintest idea what it's even about.
Robert Novak, frequent target of Take Thats due to his role in the Valerie Plame affair, was asked in an interview whether he'd ever seen The Daily Show or any of its material on him; he said no, then promptly went on to describe Jon as "self-righteous" and a "phony" and so forth. The old incident of Geraldo Rivera ranting to Bill O'Reilly about how TDS and TCR "exist in a small little place where they count for nothing" is most likely also an example, since he cited their supposed use of "video of old ladies slipping on ice and people laughing," which are not exactly Stewart and Colbert's stock in trade. (We would say these were in-universe examples, except y'know, it happened in thisuniverse).
Jon Stewart also lampshaded this in regards to Noah, with FOX complaining about it using the word "Creator" instead of "God". Jon Stewart points out that in the movie, Noah's son says that the Creator is God. It is then taken a step further with some of their complaints showing that they must not have read the source material either.
In Newhart, the townspeople think Dick's do-it-yourself books helped a prison break. They get ready to do some book burning, but then Joanna convinces them to actually read his books. They see the books couldn't have told the prisoners how to escape, but the books are boring, so they almost burn the books for that reason. So this was a Zig Zagged Trope.
The gaming magazine GameBro in Homestuck gives a so-so review to the highly anticipated Sburb. It later turns out that the reviewer hasn't even touched it.
Scrambled Eggs: Quint hates Jimmy Zoopie-Doo purely because of overexposure and his own lack of faith that teen singers can produce quality songs; the only Zoopie-Doo song he ever heard was a Gee cast member's cover, which to Quint's credit, has pretty awful lyrics.
DVD-R Hell: Rock: It's Your Decision did some terrible research on the songs it vilified. Brad quickly called the movie out for this, debunking each and every one of the movie's arguments. A particularly bad example on the movie's part:
Game Grumps: During Silver's Radical Train, Arin and Jon have a long conversation about Bioshock Infinite that lasts about two episodes, with Arin being critical of it despite having barely played it. Two weeks later, once Arin had actually finished it, he tweeted that he liked it.
He received criticism for reviewing Thomas And The Magic Railroad and stating that he has never seen the show the movie was based on. This is featured in his third "Top 11 Fuck Ups" video and he states that he has done this before (like his Pokemon review mentioned above) and he received a lot of requests by fans to review the movie so he did.
Lampshaded in that he's never actually played Final Fantasy IX, beyond maybe two hours, but avoided it solely because he hated the art style, and hadn't been paying any attention to the first two hours, since he wrote Zidane off as an "androgynous-whiny-pansy-ass character". He also admitted that "it was likely that [he] was being fiercely unfair" to Final Fantasy IX on judging it by its art style, especially when the game was specifically targeted at fans of the NES and Super Nintendo-era Final Fantasy games like him, but he just couldn't get over it. He elaborated in his Q&A at MAGfest, and admitted his reasons for avoiding it were entirely childish, and he really can't stand the art style so much that he simply can't make himself keep playing. invoked
Also admitted to never playing the Worlds of Ultima spin-off games because they were based on the Ultima VI game engine, which he hated.
In his (alternate) Worst Films of 2010 list, he included Little Fockers just because he hated the jokes in previous movies involving Ben Stiller's character's name. He admitted to never even watching it. By alternate, we mean Spoony compiled a second list of movies that would be horrible and would probably be on his main list if he managed to watch them. Included were BloodRayne 3 and The Nutcracker in 3-D.
Stuart Ashen: In the 2012 Halloween special the Silver Skull reviews a number of horror films sold in Poundland despite not having seen any of them.
Lauren Faust: When I took the job, I braced myself for criticism, expecting many people — without even watching the show — to instantly label it girly, stupid, cheap, for babies or an evil corporate commercial. I encourage skeptics like this to watch My Little Pony: Friendship Is Magic with an open mind. If I'm doing my job right, I think you'll be surprised.
Candace is examining a row of books with no visible titles Candace: Boring, dull, stupid, lame, heavy-handed and derivitive. Mom: Oh, thank you for those insightful reviews of books... you haven't read.