But should they? The Ramadi defeat only confirmed what New Zealand military and government officials already knew - the Kiwi mission was always a high-risk one.
But there is no easy option. The rise of Isis is a danger to all states. Its barbarism - beheadings, abuse of women, and cruelty to ethnic and religious groups - can only be ignored at our collective peril.
The challenge of Isis is not confined to the Middle East, and its sophisticated use of the internet to recruit supporters and activists globally point to this reality.
While the threat of Isis-inspired terrorist activities in New Zealand remains low, it would be wrong to believe New Zealand does not have a strong interest in countering its rise.
In its successful campaign for a United Nations Security Council seat, the Key Government slammed the "paralysis" of the UN in dealing with major international problems such as Isis and pledged to give voice to the views and interests of small states. New Zealand can walk away from the anti-Isis campaign but it should not imagine it would enhance this country's national security. On the contrary, hastily withdrawing Kiwi troops would diplomatically compromise New Zealand's commitment to uphold human rights and could be seen abroad as a victory for the brutal antics of Isis.
Critics argue the New Zealand troop contingent, in any event, is too small to make a major difference to the Iraqi army.
That may be true, but it is vital that New Zealand and other smaller states demonstrate their international solidarity with the victims and targets of Isis' terror. Relying on the great powers alone to address political challenges like Isis will no longer work.
In fact, the impact of the great powers has been part of the Isis problem. The US invasion of Iraq in 2003 and Russian support for the Assad regime since 2011 both played a part in the emergence of Isis as a formidable force.
It is important that New Zealand plays its part in impressing on Isis that its activities are firmly opposed by the rest of the world. New Zealand should press for the Security Council to authorise the possible use of force against Isis. At the same time, New Zealand and other like-minded states must intensify efforts to reduce the appeal of the ideas that inspire the violence of groups like Isis.
To date, Russia has blocked Security Council efforts to stabilise Syria's civil war and generously armed the Assad regime. But this has inflated the Islamist threat in Syria and Iraq, and efforts to facilitate a political transition in Syria should restart.
New Zealand must also press for a two-state solution to the Israeli-Palestinian conflict, even if it ruffles US feathers.
In short, the Kiwi troop presence in Iraq must be part of a broader multi-pronged effort to change the political conditions in the Middle East that helped generate the rapid rise of the Isis threat.
Robert G. Patman is Professor of International Relations at the University of Otago and co-director of the 50th Otago Foreign Policy School from June 26-28.