The problem is that most people don't want to be told the truth, they want to be told that the beliefs they already hold are correct. Say that a browser extensi

The problem is that most people don't want to be told the truth, they want to be told that the beliefs they already hold are correct. Say that a browser extension doing what you're suggesting existed. When you open up the Fox News site, it would say something like "this site is highly biased and often blatantly lies about political issues to give them a pro-Republican slant". Do you think that Republicans would see that as a sign that they should stop reading Fox News? No, they would just disable the extension.