An optical illusion

Back in the early days of baseball, there were folks that claimed that a curve ball didn't really curve, that it was an optical illusion. In reality, they were partially correct in that what you are seeing is the deviation of the flight of the ball from the pure parabolic path your mind expects. So, for instance, a "rising" fast ball is quite impossible; it's really just that it doesn't fall as quickly as your mind expects.

If all the major news outlets are heavily tilted to the left and favor the Democrats and its been this way for so long, everyone intuitively expects it to be the case and one cable news channel appears that is actually quite "fair and balanced," then you can be sure that it will appear, to the untrained observer, to tilt strongly to the right.