Ramayana was an Hindu epic which herofies Hindu/Aryan god Rama; Kambar, an ancient Tamil poet has translated it into a Tamil version named Kambaramayanam.
According to the Ramayana, Rama is a hero and the Ravana is a villain.
Certain historians have interpreted that Rama was an Aryan and Ravana was a Dravidian. Moreover, some linguistic experts and historians justified that Ramayana was written by Aryans to humiliate Dravidians; they explained that the Dravidians are depicted as Monkeys and Rakshasha. This led a strong angry stir against the Hindu ideologies especially by Dravidian supporters.
Because of the said reasons, Annadurai was criticizing Kambar, the ancient poet who translated Ramayana into Tamil. Anna has written a book called Kambarasam, in which he thoroughly and linguistically criticized the characters of Rama and his obscene characteristics as depicted in Kambaramayanam. The book is one of the very strong Dravidian book that reflects Dravidian sentiments.