Hi John! I think you are completely correct in being mad about this, you were being conscience not reckless. I have actually been told this before because I am a frequent coffee drinker as well, but I was at a dunkin donuts not at school. They told me I couldn't give them the cup I just used to refill it with another ice coffee... I was confused but just went with it. Maybe this is a sign that you should invent a special cup for school to use so students can refill their drink in a sanitary way, then become rich!