Similar to a Carpet Bagger, a milk bagger is a person who is hated by the general population, and does change the milk. Said "Milk Bagger" is someone who will drink the rest of the bag of milk, and they will put it back in the fridge. This person must be dealt with by being given the asshat treatment.
Joe just chugged the rest of the milk and shoved it to the back of the fridge. What a dirty milk bagger.
One who voluntarily gives up their own freedom and liberties so they may suck off the teet of the American government from cradle to grave; A follower of the teachings of Karl Marx; a person who believes other tax paying citizens OWE them a hand-out to purchase food, housing, an education, health insurance and other life commodities.)
Obama and his Commie friends love their milkbagger constituents because they are too stupid to realize they are giving up their freedom and liberties to help an oppressive government gain power.