Yes, he was trying to convert the public to Roman Catholic Christianity.
http://www.reidsguides.com/destinations/europe/italy/lazio/rome/sights/vatican_sistine.html
As the earlier Tuscan genius Dante had done to his political enemies in his poetic masterpiece Inferno, so Michelangelo put Cesena into his own vision of Hell, giving him jackass ears and painting in a serpent eternally biting off his testicles. Furious, Cesena demanded that the pope order the artist to paint his face out, to which a bemused Pope Paul III reportedly replied “I might have released you from Purgatory, but over Hell I have no power.”