The phrase "sang the praises" typically means to enthusiastically extol someone or something. However, antonyms for this phrase include criticism, condemnation, disapproval, and censure. If someone is singing the praises of a particular product, for example, the opposite would be to criticize the product, find faults with it or condemn it outright. To withhold praise, ignore or dismiss something as unworthy are also possible antonyms. It is important to remember that antonyms depict the opposite of a given word or phrase, and in this case depicts the exact opposite of singing praises.