Instructions
Scroll left or right to the "Game" icon in your XMB menu. The "Game" icon is represented by a picture of a controller.
Scroll up or down to the "Game Data Utility" folder in your XMB menu. The "Game Data Utility" folder is represented by a picture of a folder and is marked with the words, Game Data Utility.
Press the "X" button to access the "Game Data Utility" folder. The "Game Data Utility" folder holds all of the saved settings for your games.
Scroll up or down until you have found the game data utility for the DLC you wish to delete. DLC will often have its own specific file. If the DLC doesn't have its own file, it is located within the utility file from which the DLC originates.
Press the triangle button to delete the file. The action will bring up a window asking you if you are sure that you want to delete the file.
Scroll left to the word "Yes" and press the "X" button. If the DLC you are deleting is inside the game's utility data, you will need to reinstall the game data once you play the game again.