Freudian slip, perhaps?
I remember hearing a post-retirement radio interview with one of the "old school" TV reporters - I THINK it was David Brinkley, but I couldn't swear to it.
He said that the reason TV reporters don't cover stories impartially is because they really, really think it's their job to guide the audience to the RIGHT conclusions, and sometimes persuasive arguments from the WRONG side might confuse the audience, or even make them form WRONG opinions.
And he said they're not conspiring to do this - they really, really think THEY are the custodians of the truth, and it's their responsibility to make sure the public sees the light as they do.