Misattributed
Source: This quote, frequently attributed to Aquinas, is actually a paraphrase of a passage (itself an elaborate paraphrase of Augustine) by Ptolemy of Lucca in his continuation of an unfinished work by Aquinas. The passage from Ptolemy reads: "Thus, Augustine says that a whore acts in the world as the bilge in a ship or the sewer in a palace: 'Remove the sewer, and you will fill the palace with a stench.' Similarly, concerning the bilge, he says: 'Take away whores from the world, and you will fill it with sodomy.'" (Ptolemy of Lucca and Thomas Aquinas, On the Government of Rulers, trans. James M. Blythe. Philadelphia: University of Pennsylvania Press, 1997, 4. 14. 6). What Augustine actually wrote (in De ordine, 2. 4. 12) was simply: "Remove prostitutes from human affairs and you will unsettle everything on account of lusts." Only Book 1 and the first four chapters of Book 2 of On the Government of Rulers (De Regimine Principum) are by Aquinas. The rest of the work was written by Ptolemy. (It even mentions the coronation of Albert I of Hapsburg, an event that occurred in 1298, twenty-four years after Aquinas's death.) The quote comes from Book 4, which was definitely not written by Aquinas.
