Thrilla in Manila is a new documentary currently airing on HBO. It follows Muhammad Ali and Joe Frazier from their friendship to their falling out to, eventually, their third and final bout in Manila, Philippines. Whether or not you’re a fan of boxing (I am), it’s definitely worth checking out.

Ali is one of the most revered figures in sports, and for good reason. Not only was he one of the flashiest, most decorated and outspoken athletes who ever lived, he also challenged America’s view of race during one of America’s most tumultuous times. Ali deserves the respect he gets. To many, he was a hero, and I would suspect that even those who cheered against him owe him begrudging respect.

But if comic books taught me anything, a good hero is nothing without a good enemy. Enter Frazier, Ali’s most bitter rival.

The documentary focuses mainly on Frazier, the less loquacious of the two boxers. It also shows a side of Ali many may be apprehensive to acknowledge: a dark and troubling side. Ali, known for his verbal (and physical) bravado, may have delighted fans with his over-the-top taunts and insults, but, as the documentary portrays, these comments may not have been without their malicious undertones. File footage of Ali talking about speaking at a KKK meeting, inter-cut with footage of a burning cross, producers a chilling effect. A much quieter, and more natural moment, of Frazier as an old man, watching and commenting on a video of the fight from which the documentary takes its name, is just as powerful–if not more so.

Well worth a look for anyone interested in sports, documentaries or America’s sad history of racial injustice.