Everyone is biased. It's natural.
Everyone also likes to be agreed with. That's natural too.
That's why most peoples main news source is from an agreeable medium. Sure, we all listen/watch what the other side thinks, but we much prefer the one that's in our corner.
This is compoundedly true of soldiers in war. Their lives, and the lives of their comrades depend on their skill, enthusiasm, and morale. It doesn't do a unit good to watch how evil the war is, how the coalition is being slaughtered at every turn.