The late-night legend took aim at his former network home and David Ellison's media company, speculating that Colbert's show was canceled for political reasons.

While ratings for Colbert's show have declined over the last decade, the program has consistently achieved the highest views of any show in the 11:35 p.m. hour, outdrawing ABC's "Jimmy Kimmel Live" and NBC's "The Tonight Show Starring Jimmy Fallon," according to Nielsen.

David Letterman delivered a fiery rant against CBS and parent company Paramount for cancelling Stephen Colbert’s “Late Show,” calling the decision “gutless” and “pure cowardice” as he labeled his successor a martyr of the network.