It's all a horse race
The Cheney flap over the hunting accident proves one adage about liberals. Every aspect of modern life is to be viewed as a horse race. They goal is to defeat conservative/Republicans. If an event can make that happen it will be embraced.
The cartoon crisis is the opposite. Since there is no way to use this to hurt Bush/Republicans, there is no need to focus any attention on it.
The flap of Cheney seems to be that he waited alert the media. First of all he has no requirement at all to alert the media. Second the priority in this case has to be to get medical attention to the injured person.
The media showed no such indignation over the White House delay in the Vince Foster affair. They explanation of the difference can only be the horse race.