In reasonable people you can assume a degree of psychological integration. They probably believe what they say. It's hard to function otherwise.
Is it safe to assume the same of media outlets? My intuition says no. Management sets the tone and the editorial position. Editors and staff execute. That provides ample room for what would be psychotic behavior if management, the editors and staff were all one person.
Reasonable people can differ only if their prior information is different. Or, "People with the same priors cannot agree to disagree.", as put by Robert J. Aumann here: http://www.jstor.org/pss/2958591
> Reasonable people can differ only if their prior information is different.
Disagree entirely.
When evaluating complex choices in a chaotic world, we humans use tons of heuristics. There are a lot of things that aren't quantifiable information, but still allow two rational people to reach different conclusions: models of the universe, weight attached to different speakers, moral stances, worldviews, etc.
I think people can only agree to disagree when they can see past their differences. If it's something like which are better, tomatoes or potatoes, then it is easy. If it is something deeper to one's center like PC or Mac, or some programming language then it's harder, and conflict can end up huge if it's over life and death or reputation building. In mostly anonymous and almost random meetings, such as HN, agreeing to disagree is hard, and more often than not, conflict or alliance is expressed through moderation rather than enmity or camaraderie.
At the end of the day, I tend to view argument as vulgar, but put up with it in striving for truth.
Restating:
"Don't leap to assume the worst of others".
or
"People can come to different conclusions honestly - disagreeing with you does not mean that they are venal".
or
"Reasonable people can differ".