Joe Biden began his speech to Rev. Jesse Jackson’s civil rights organization with a strong rebuke of the most-talked-about moment of the Democrats’ debate when Sen. Kamala D. Harris skewered his past stance against federally mandating the busing of black children to white schools.

“I heard, and I listened to, and I respect Sen. Harris,” Biden said Friday. “But we all know that 30 seconds to 60 seconds on a campaign debate can’t do justice to a lifetime committed to civil rights.”

The former vice president told the majority black audience that he’d “fought my heart out” on issues of racial equality. He said he never opposed voluntary busing. However, statements he made in the 1970s show that he was opposed to sending white children to majority-black schools and black children to majority-white schools.

Harris, the only African American on the stage Thursday night, told Biden that his previous position against busing and his recent comments about working with segregationist senators in the early part of his political career were hurtful because she was one of the little girls who benefited from busing.

Biden said he worked to address the “root causes of segregation in our schools” and that he had “always been in favor of using federal authority to overcome state-initiated segregation,” adding that civil rights aren’t up to the states, but are a constitutional protection.

“That’s always been my position and why I ran for federal office in the first place,” Biden said.

Biden then pivoted to the work he and President Barack Obama did on commuting drug sentences. With even more forcefulness than he showed speaking about himself, he offered a full-throated defense of his former boss.

“With all due respect, my president gets much too little credit for all he did. I’m tired of hearing about what he didn’t do,” Biden said. “This man had a backbone like a ramrod.”

Biden also brought up the protests by self-proclaimed white nationalist in Charlottesville in August 2017 — an event he has cited as his catalyst for running against President Trump, and lambasted Trump for never fully condemning the self-professed neo-Nazis and white supremacists that day.