Again, "actual malice" doesn't mean "acting maliciously" in the colloquial sense. It's a legal term of art from the aforementioned NYT v. Sullivan case and is explicitly defined as "with knowledge that it was false or with reckless disregard of whether it was false or not." Publications leave up articles they know to contain falsehoods (that were believed to be true at the time they were written) all the time. Unless libel (and therefore actual malice) is shown, I don't know of any precedent that would imply an obligation to issue a retraction.
