But when the insult is levelled by the previously supportive Haaretz newspaper, standard-bearer of the country’s liberal-Left, it may be time for him – and by extension, President Barack Obama – to take notice.
The withering description was coined by Barack Ravid, the paper’s well-informed and normally restrained diplomatic editor, to describe Mr Kerry’s attempts at brokering a truce to the bloody conflict in Gaza – rejected by Israel amid widespread mockery.
“It’s as if he isn’t the foreign minister of the world’s most powerful nation, but an alien, who just disembarked his spaceship in the Mideast,” wrote Mr Ravid, even while softening his remarks by describing Mr Kerry as “a true friend to Israel”.
Worse still from Mr Kerry’s viewpoint, the journalist suggested that, Moshe Ya’alon, the Israeli defence minister, “may have had a point” earlier this year when he labelled America’s top diplomat “obsessive and messianic” in remarks that were widely disparaged at the time over his abortive attempts to mediate a peace deal with the Palestinians.
The Israeli media carried similarly mocking depictions in abundance on Sunday – all fuelled by senior figures in Benjamin Netanyahu’s government, who professed amazement at the terms of a proposed ceasefire deal which they said were skewed in favour of Hamas, the Islamist militant group which Israel is fighting.
Writing in Maariv, Ben Caspit called the US secretary of state “an ongoing embarrassment, with the characteristics of a snowball. The further he rolls, the greater the embarrassment”.
Yet it is the Haaretz insult that signals Mr Kerry’s credibility loss in the eyes of Washington’s closest Middle East ally, according to Israeli government insiders.
“If he gets rubbished by Haaretz, it means he really goofed up,” said one official, who said the criticism was widely shared across the Israeli political spectrum.
Central to it was Mr Kerry’s apparent decision to use Qatar as a conduit through which to communicate with Hamas, effectively ditching an earlier Egyptian proposal which the group had rejected. The result, according to a separate report in Haaretz, was a draft ceasefire arrangement that made no mention of requiring the destruction of tunnels that Israel says have been dug to carry out attacks on its citizens or of depriving Hamas of its rockets and missiles.
Having trumpeted the proposal as major progress, Mr Kerry later told reporters during a high-profile visit to Cairo that Israel had not rejected it – a claim which officials say was effectively untrue.
“What no one can understand is how he can reject the consensus that’s been built between the Egyptians, the PA [Palestinian Authority], Israel and Saudi Arabia and just go to Qatar,” the official said. “America’s allies were all backing Egypt’s ceasefire plan. It was the only game in town. But he turns to a state that’s no more than a gas bubble with a vote at the UN and that has always supported Hamas, the Muslim Brotherhood and all those madmen fighting in Syria.”
The secretary of state, he concluded, was “wasting his capital” as the supreme diplomatic representative of the world’s sole “irreplaceable superpower”.
Some of this may be payback for what has been seen in Israeli eyes as previous diplomatic gaffes committed by Mr Kerry – such as warning that Israel would face a future campaign of de-legitimisation or evolve into an apartheid state if it failed to make peace with the Palestinians.
But the barely-concealed disdain it betrays hardly bodes well for his prospects of rescuing Gaza from the mire of bloodshed into which it has sunk.