Pretty much all gamers have an example of it in their own lives. Try to picture this—you buy a game that looks really cool on the shelf, go home, and realize that it’s actually not as awesome as you initially thought. When I was younger, this usually meant getting an N64 or GameCube game based on recognizing a character or knowing a license (THQ!), and I was burned a few times on some games I expected to be a lot better than they turned out to be.
Because games are art, and everyone's tastes are different. Just because a majority of people didn't like a game, doesn't mean it can't be good to someone else. How about letting people have their own opinions without trying to tell them that they're wrong because they like something they shouldn't.
Two reasons:
1) Some of the people who got hyped, swore the game would be 10/10 material, shelled out $60 on a brand-new game and then found out it sucks don't want to openly admit that they're stupid for betting on the wrong horse
2) Because "terrible" is subjective, just like "amazing". Personally, I think Bioshock Infinite is average. A lot of people think it's "amazing". Who is right? Both of us, and neither of us. It's just an opinion.
If you read my piece, you'll see that I actually mention that it's good to find the fun in everything, but that if we push companies to produce better products, we'll all be better off.
Two words: Blind fanboyisms
To each their own. No matter how bad a game is, for every 1000 gamers that hate it, there will always be a handful that love it. Crazy or unbalanced as they may be.. ;)