The comments came during a marathon meeting, including six panels examining the Supreme Court nomination process, the composition of the court and more. Conservatives on those panels, meanwhile, retorted that it is actually progressives' calls to pack the court that will harm its legitimacy beyond repair.
The meeting was the third held by the commission, which is tasked with producing a report for the president later this year on the status of the debate over the U.S. court system and potential reforms to so.
Nan Aron, the president of the progressive Alliance for Justice, accused Republicans of hypocrisy for how they confirmed Justices Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett, and accused those justices of bias.
"It would be one thing if these justices then turned around and were fair and impartial. However, in scores of democracy cases, they've consistently undermined democracy and aided the very party that appointed them," she said. "Republicans are using this undemocratic and partisan majority on the court to cement their own power."
Thus, Aron concluded, "If the court day after day continues to bend the law to side with the wealthy and powerful… then the only possible conclusion is that reform is imperative."
"Unless there are real reforms to the court, including expanding the number of justices, something completely constitutional and done regularly throughout our history, our system of government and our rights and legal protections will be eroded for generations," Aron said.
Christopher Kang, the co-founder and chief counsel of the pro-court-packing group Demand Justice, alleged that he saw Republicans "steal a Supreme Court seat from President Obama," and called it a "fiction" that there is an "independent judiciary" that should be elevated above politics.
"Our democracy is under assault by this Supreme Court," Kang said. "So we cannot evaluate reform proposals under a rubric of whether or not they will preserve this court… We need to expand the Supreme Court."
The Biden commission also took testimony from some right-leaning voices.
Ilya Shapiro of the libertarian Cato Institute decried the Supreme Court confirmation process as the fundamental cause of the court's ills, calling it "Kabuki theater." He suggested an end to confirmation hearings altogether and reducing the size of the federal government – and therefore the Supreme Court's importance.
"The fundamental problem is the politicization not of the process, but of the product," Shapiro added. "The reason we have these heated battles is that the federal government is making too many decisions for such a large, diverse, pluralistic country."