When a person wanted to stay calm, they remained relatively unfazed by angry people, but if they wanted to feel angry, they were highly influenced by angry people.
The nature of the class, the Intensity and difficulty will vary based on the instructor but a couple of things you can expect are an awesome soundtrack, the opportunity for some emotional release, and to walk out feeling a little more "aggressively-empowered".
Think about how often you tell white lies to protect someone from the pain of the truth? New research from the University of Chicago indicates that perhaps you should stop doing that.