Having once been in a print news organization (but not broadcast), I'd speculate there was huge discussion about this story at CBS before they ran with it. Its potential gravity would have gained the attention of many senior editors, several top reporters, and perhaps even the management heirarchy at CBS (as a heads-up, but not to engage in the editorial discussion).
It's inconceivable that at least a few of these folks wouldn't have raised red flags about the authenticy of the docs. Some might even have been professionally livid about the apparent lack of even rudimentary vetting.
It would have taken one or more big guns to make the decision to run with the story, and by big guns you'd have to include Rather, since it's his rep that's ultimately on the line.
So under this scenario (which experience tells me is realistic), Rather discarded even the most basic and rudimentary exercise of news judgement to run with this story.
One can only attribute such a flagrant oversight to one thing alone: he's going senile.