CAMBRIDGE - Milk is our first and most basic food. In recent years. there’s been a contentious and emotional debate over how we are allowed to consume it. Raw milk - unpasteurized and whole with its purported health and taste benefits - is on one side. On the other is pasteurized milk: the modern heavyweight champion of food safety. Raw milk proponents have been portrayed as oblivious hippies who are tempting bacterial fate. Defenders of pasteurization, in turn, are cast as nanny-state corporatists with unsophisticated taste. Each side charges the other with misunderstanding health, freedom, parenting, and - among other issues - what it means to be American. Last Thursday night, Harvard Law School hosted a debate between leading thinkers on each side of the issue. It was not disappointing.