I think any news source can have this problem. It should be expected that a news outlet will release a bad story - like it should be expected that a trader lose money from time to time.
A legitimate news firm will have infrequent missteps and will respond appripriately when they do. I think CNN responded appropriately with a loud response and the firing of the three involved.
I'm sure you can think of many other "news outlets" that would not have done the same.
It should not be expected that a "news" outlet would be so overtly biased and release fake story after fake story.
CNN is responding in the way they are because they finally have no choice - they have reached the level where they need to do something to gain back the trust of the public and other organizations, or else they are toast.