It's rude to eat food that doesn't belong to you.
Andy and Bobby are roommates that share a refrigerator and kitchen.
Bobby wants to make himself something as a late night snack.
Bobby makes himself a sandwich for his midnight snack, leaving Andy's ice cream alone.
Bobby makes himself a late night snack which happens to be Andy's ice cream and eats it.
Bobby is full and has a nice night sleep after eating.
Bobby gets very sick from eating Andy's ice cream as Andy put laxatives in it.