Howard usually doesn't appear on a talk show unless he meets with his psychiatrist first, which might explain his rant. He goes off about Conan, The Tonight Show, and Late Night after calling himself a "student of late night television."
Despite the many "truth bombs" dropped, Howard makes some good points. Later, he played "Louie, Louie" with the Roots, in what might actually be his big farewell to the Late Night talk show circuit.
[There was a video here]