No. even if it was an apology (which any child could tell it was not), it would not be good to "mend fences." Mending fences, making peace, is not always good. Sometimes, it serves evil, as it would in this case, because it would not acknowledge the deliberate malice of the slander, and the intent to harm the innocent.
Letterman needs to be fired. Period. Anything less is groveling to evil.
This is not an isolated commission of hate-language by Lecherman.