David Bernstein at the Volokh Conspiracy writes:
Mearsheimer accuses his critics of suggesting that he must be an anti-Semite, given that he is intellectually in bed, so to speak, with the likes of Gilad Atzmon. Certainly, it's reasonable to suspect Mearsheimer of anti-Semitism as this point, given that the main alternative explanation, that he is simply a fool who endorses highly polemical books attacking Jews and Israel without reading them closely or knowing anything about the author, has now been rebutted by Mearsheimer himself. But one could also posit Mearsheimer has decided to adopt a "Popular Front Strategy", willing to accept any anti-Israel allies even from the blatantly anti-Semitic fringe. Regardless, it's a pathetic fall from grace for Mearsheimer, and it's disappointing to see that his co-author Walt is enabling him rather than pulling him back from the brink.
UPDATE: Or perhaps Mearsheimer simply agrees with this charming quote from Atzmon: "Because Anti-Semite is an empty signifier, no one actually can be an Anti-Semite and this includes me of course."
And while we're at it, Mearsheimer also defends Atzmon from the charge of being a Holocaust denier. Here's a quote from Atzmon that I found on his own website: "I must admit that I have many doubts concerning the Zionist Holocaust narrative. Being familiar with many of the discrepancies within the forcefully imposed narrative, being fully familiar with the devastating tale of the extensive collaboration between the Nazis and the Zionists before and throughout the Second World War, I know pretty well that the official Holocaust narrative is there to conceal rather than to reveal any truth." Res ipsa loquitur.