Kissinger was a drama queen prone to petulant and unprofessional behavior. I bet there are senior FO Staff who where burned by him back in the 70's - and I bet there's a few now senior members of the state department who feel the same.
I can't speak of his personal behavior. I've never been in a room with him nor read any accounts of that. However, dismissing his expertise as simple "flattery" without really breaking it down is dishonest. Kissinger has a track record of being quite successful. I know some countries came out worse because of him but it doesn't diminish his insights.
I haven't read Luttwak's book but he seems like a smart guy. I hope in the book he does more than just call it "flattery" and talk about Kissinger's wife, which is what the linked article does. My guess is that Luttwak breaks down Kissinger's ideas. My problem isn't with Luttwak or his book. I haven't read it to be able to judge. I just don't like this article and I think it doesn't do a good job of advancing Luttwak's idea. Why would he even deviate into personal things about Kissinger like his wife?