We were told also that you have cereal with milk or yogurt so that you don't use it as a mindless snack. In fact if you read the whole Core list, you'll note that most of the foods require sitting down and paying attiont while eating them - very few except fruits are things you can eat with your hands. By being mindful of what you're eating, you eat less. That being said, if you don't like milk, but you still sit down and eat your cereal from a bowl with a spoon, I'd say you've met the spirit of the program if not the actual rule!
And, honestly, there are no WW police who are going to come and haul you off for not eating your cereal with milk/yogurt! The same as they are not going to get me for eating Cheerios as core, when technically they are not.