"I can get real mad. The demons come out of me." – Joe Joe "Butterbean" Sweeney says he’s had "about 2000" street fights. He had a rough upbringing, but says his dirty street fighting days are behind him. Marcelo "Machine" Altieri is a professional Mixed Martial Arts fighter. He says MMA has taught him discipline. Paul Diacogiorgis is a senior business manager who recently had his very first fight. He competed in Melbourne’s "Executive Fight Club" alongside other like-minded white collar professionals. This week, Insight asks why some men fight. Following Daniel Christie’s death from a 'coward punch’ in King’s Cross on New Year’s Eve, and the introduction of the 'one punch’ law in NSW, Jenny Brockie explores what’s behind the urge to land a blow. Are there any rules when fights take place outside the ring?