Character assassination is an old practice familiar to those on the hard left. The tactics are simple - evoke dark motives for your opponents' actions and seek to discredit them rather than engaging a political issue on its merits.
It matters little, of course, that Communist agitators came to master the practice - in the age of mass communication, totalitarian regimes from left and right alike have relied on this technique to besmirch their enemies. A totalitarian mindset will always skirt an issue and seek instead to discredit an adversary by insinuating sinister plots.
Antisemitism takes the pride of place in the history of such vile arguments - and the accusation of dual loyalty thrown at Jews throughout the ages and at Israel supporters in recent times is in this fine tradition of rhetorical cowardice.
In brief, to suggest that supporters of Israel are agents of a foreign power whose interests are not aligned with those of the government of the country in which they reside is not an argument over the merits of a policy.
For who settled the question of national interests upon which this accusation rests, after all? Calling on governments to build, cement and nurture a thriving strategic rapport with Israel is never blind defence of every single policy Israel pursues - as accusers of Israel's supporters insinuate despite the glaring lack of evidence. It is a reasoned argument about interests, values, costs and benefits.
What do detractors of such an alliance have to countenance?
In recent weeks, the accusation that pro-Israel organisations in the United States are "Israel firsters" has forcefully returned to the surface of public debate in America, thanks to Media Matter's pundit, MJ Rosenberg, who is making news by insulting any Jews who fail to agree with his views. No doubt he will earn thoughtfully approving nods from the "Israel lasters" and "Israel nevers" brigades among the European commentariat, because those who embrace the rhetoric of antisemitism in order to bash Israel, these days are, apparently, courageous, as long as they are called Rosenberg or some other Jewish sounding name (however, alas, less so if they are called Smith, or White).
Rosenberg has doubled down on the accusation as he crusades against pro-Israel lobbying group Aipac on behalf of a leftist organisation called Media Matters. He argued: "Saying Aipac is guilty of dual loyalty is giving it credit for one more loyalty than it holds."
He has in return been savagely attacked by veteran lawyer and Israel advocate Alan Dershowitz and others.
The truth is that Rosenberg, and those like him who devote considerable time and energies questioning the patriotism of pro-Israel supporters in the West have no loyalty to the democratic values on which their nation and its foreign policy stands.
Aipac and its European counterparts wish to engage the foreign policy debate on its merits. Rosenberg and his intellectual fellow travellers wish to smear them into silence by evoking Western civilisation's oldest and most irrational hatred. Who is un-American here?