Well, they will. Most students do not know how to think critically, and when you introduce those skills to them and require that they do this, for many, it threatens a worldview created by soundbites and hysteria.
No one likes to have their worldview threatened, no matter how flimsy the foundation it rests upon. In fact, the flimsier the foundation of the idiotic, fear-based, sound-bite developed worldview - the more defensive students will become when and if you challenge it. I was an adjunct for years at a community college; and consistently saw critical thinkers tapping out at about 10 to 25% of my classroom population.
But, the more disturbing trend was the increasing percentages of students making pretty idiotic assertions that they held as uncontestable fact. More and more, my students felt extremely comfortable saying any crazy thing, that they picked up — oh I don’t know just anywhere, Wikapedia, Fox News, Facebook- and positing that it was 100% true.
Where is your evidence? What is the source of this information? Is your source reliable? Is your source unbiased? These questions I raised may as well been posed in a foreign language given my students familiarity with them. Debates were the method I used to teach critical thinking, and avoid allegations of bias. Debates have two sides, each side has valid points- BUT I required that points raised actually be valid- which meant citing at least The New York Times - not your average Grand Master KKK Wizard Joe as the source of your information.