There is a exception for parents travelling with an infant from the liquid restrictions. Without the infant there is no immediate need to have milk. The rules are quite clear.
It was humiliating, horrifying, as I was standing there crying, pleading,
This sounds like a massive overreaction to a fairly straightforward situation that is in force in most of the world's airports. The TSA document linked in this thread does not explicitly state you must be travelling with an infant or toddler however it is definitely implied.
Without the child at hand then breast milk is just another liquid and is treated accordingly.