The comments came as a federal appeals court panel heard arguments in the case, in which Apple was found to have colluded with publishers to raise e-book prices.
Apple argues that its entry into the e-book market was pro-competitive because it challenged Amazon, which had a dominant share in e-books.
Apple claims its entry spurred additional publishers to produce e-books, and that prices of e-books generally fell even though it concedes that some prices rose in the short-term.
But today, one of the judges on the three-member appeals panel appeared openly hostile to the government's case.
Judge Dennis Jacobs questioned a Department of Justice attorney on the agency's hostility to Apple's challenge to Amazon, which had more than estimated 90 percent market share at the time.
"What we're talking about is a new entrant who is breaking the hold of a market by a monopolist who is maintaining its hold by what is arguably predatory pricing," Jacobs said.
He defended the government's case on the grounds that Apple's entry raised e-book prices for many consumers.
A ruling by the appeals panel is expected in 2015.
