Belden was born to Jewish parents in San Francisco and grew up in Corte Madera, California. His father is a journalist at a local TV station, and his brother works in tech. His mother died by suicide when he was six years old. Belden has said he was "a troubled teen" and went to five different high schools, including a boot camp from which he ran away before being arrested for public intoxication in Mission Dolores Park. Belden has identified as a Marxist since his teenage years and protested the Iraq War when he was thirteen. In 2005, when he was fifteen, he and his friends started a satirical right-wing, pro-war punk band called Warkrime. His stage name in the band was President Chaos. They released their first album, "Give War A Chance", in 2006, and the band broke up in 2008. After Warkrime, Belden played bass in Wild Thing, another punk band based in San Francisco where he adopted the "'Bad Boy' Brace Belden" nickname.