Watch Football’s Most Dangerous Rivalry (2012) : Full Movie Online Free The rivalry between football clubs Rangers and Celtic goes past typical name calling and dives into violence, racial slurs and pure hatred. The rivalry between Glasgow's "Old Firm" sides is the most famous in world football. It's the game's flagship loathing, proof of the power of the sport to inspire profound levels of tribal loyalty and a near-Pavlovian revulsion at anything to do with a rival. We examine the situation and try to get a handle on the political, religious, and national identity clashes that have shaped the rivalry, speak to fanzine editors on both sides of the divide and travel with the Bhoys' away support to a match at Tannadice.