Kudos to the Public Editor for addressing the issue, but this never should have happened.
"Yes, the claim was "out there" but so are smears of all kinds as well as claims that the earth is flat and that climate change is unfounded. This one comes from the author of a book on the same subject with an opposing political orientation. By taking it seriously, The Times conferred a legitimacy on the accusation it would not otherwise have had. And while it is true that Mr. Perlstein and his publisher were given plenty of opportunity to respond, that doesn't help much. It's as if The Times is saying: Here's an accusation; here's a denial; and, heck, we don't really know. We're staying out of it. Readers frequently complain to me about this he said, she said false equivalency — and for good reason. So I'm with the critics. The Times article amplified a damaging accusation of plagiarism without establishing its validity and doing so in a way that is transparent to the reader. The standard has to be higher."
Typos courtesy of my iPhone