Why/How does alcohol kill bacteria?

Alcohol kills bacteria by denaturing proteins in the bacterium. Even though water is the most common ingredient in Listerine, swishing with water for 30 seconds does not kill bacteria. Some dentists wonder whether the active ingredients are put into Listerine simply for marketing purposes; advertising a product that contains 78.2% water and 21.6% alcohol will not sell well. If it were true that the active ingredients in Listerine have little or no impact on killing bacteria, then it would be cheaper for a customer to buy a bottle of mouthrinse that contains 21.6% ethanol and no other ingredients except water