Anybody might think that Susan Rice is gearing up for a confirmation hearing. Last week, the US ambassador to the UN tweeted: “I condemn today’s cowardly terrorist attack targeting innocents on a Tel Aviv bus.” Yet trawling back through her Twitter feed over the previous week, there is no indication that innocents might be dying anywhere else in the Middle East. The word “Gaza” is noticeable by its absence – although the ambassador did find time to hail America’s Transgender Day of Remembrance.

A bit of solidarity with Israel never goes amiss if – like Ms Rice – you are quite likely to be nominated to be America’s next secretary of state. But the ambassador’s selective tweeting reflects a broader problem for US foreign policy. Even under Barack Obama, America cannot shake off the charge that its moral authority is regularly undermined by the use of double standards. Israel is not the only beneficiary. The Americans’ robust condemnation of repression in Syria, Libya and (latterly) Hosni Mubarak’s Egypt makes a striking contrast with its embarrassed muttering about Saudi-backed repression in Bahrain. The administration’s response to human rights violations by other American friends such as Rwanda or Sri Lanka has also been muted.

In the real world, American concern for human rights is always going to be balanced by other concerns – preserving alliances, avoiding conflict, flattering domestic constituencies. Given the difficulty of consistency on human rights, some might suggest that silence is a more seemly alternative. But that is no good either. Many of those who decry American double standards would be even more appalled by a US that cheerfully embraced a completely amoral foreign policy.