No one in the US dares to utter a negative evaluation of Israel and its political leaders.

I was informed about the above constraint on every US person of note from top actors, journalists and politicians.
Therefore, when an anonymous US government functionary dares to voice his frustrations, then:
U.S. Secretary of State John Kerry has publicly blasted the unnamed "senior [Obama] administration official" who recently called Israeli Prime Minister Benjamin Netanyahu a "chickens—t." Speaking to The Atlantic magazine, the official said Netanyahu "won’t do anything to reach an accommodation with the Palestinians or with the Sunni Arab states." Kerry called the remarks "disgraceful."

John Kerry: "I think we need to work quietly and effectively, and we condemn anybody who uses language such as was used in this article. It does not reflect the president. It does not reflect me. It is disgraceful and unacceptable, damaging. And I think neither President Obama nor I — I’ve never heard that word around me in the White House or anywhere. I don’t know who these anonymous people are who keep getting quoted in things, but they make life much more difficult."

You will note the last part of what Kerry says:

"they make life much more difficult"

 "they" create the condition for poor Kerry's life to be "much more difficult" because there are people in the US and in Israel who can truly make his life  "much more difficult". And these people-cannot-be-named!

I wonder who they really are? If you do, let me know, please.