It seems to me that the pile on of CBS is less an attempt for other journalists to "smear" their rivals (the pack mentality of journalism doesn't really lend itself to this kind of motivation) as much as a way for the rest of journalism to cover its butt for the status quo (see, this is why what we do really is "objective" or some such motivation).

What this is, more than an attempt to smear the Kerry campaign (grasping at straws here, but attempting to recreate a parallel scenario to the SBVT smears and the Bush campaign in the minds of the electorate), is an attempt to chill the press toward deeper investigation of this issue.  If somebody set CBS up, they are doing so to send a message to the rest of the press.