This was inappropriate behavior and the supervisor reporting it did absolutely do the right thing. It also seems to me that HR was taking appropriate action. Unfortunately there is not only a lot of sexism and harassment, but also a lot of misconception as to what constitutes what. This manager may not have harmed anyone, but he was prevented from doing any potential harm in the future. Being alone in a room with a drunk and possibly physically stronger man can be a very frightening experience. The next intern may have suffered emotional damage. Lots of people seem to underestimate the possible emotional consequences.