One fundamental aspect of digital media literacy is understanding the difference between fact and opinion. It's one of the things we teach, starting in elementary school, because it's fundamental to having any kind of reasoned debate, as you say.
Beyond dividing those two, beyond dividing whether we're discussing an opinion or facts, media literacy helps us to identify which sources of information are reliable, so it is only when we can divide opinion and fact, and when all sides of an issue are drawing from reliable, verifiable sources of information, that we can have that debate.