We should say so because we care about an international order based on rules. Every country has an interest in that order – Israel, in the long run, more than most.
It is essential that the US, in particular, keeps alight the flame of a two-state solution as and when this, the only solution, could have stronger support.
At least 13 members of his front bench are in open revolt. As I write, that’s sustainable. As matters develop, it may not be.
Sir Keir’s choice is between not sacking front bench dissenters, so inviting claims of weakness, and doing so – thus provoking accusations of over-reacting.
We should own up: we don’t put a flag in our windows because we don’t want a brick through the glass. Equally, lapel pins are out: who wants to invite abuse? Intimidated, good people are doing nothing.
As is so often the case with international law and institutions, noble ideals bely a necessarily fractious and often shabby reality.
This way of thinking also contrasts with the naive counting of the civilian dead. In this tradition, war can be a necessary evil, but that judgement requires attention to its practical consequences.
A British government which recognised the benefits of a stable, prosperous Africa and offered incentives to skilled professionals to return home would find itself lauded on the continent.
What Sir Keir and Labour MPs say in the Commons is worth keeping an eye on.
Doing so will be immensely difficult and will involve fighting in densely populated urban areas, creating enormous risks for both the Israel Defence Forces forces and Gazan civilians.
Netanyahu may have said: how would you feel, were you lectured by countries without an independent judiciary, let alone the free press, minority rights and fair elections that we have in Israel?
Earlier this year the Coalition for Global Prosperity set out to teach the next generation of Parliamentary candidates a basic knowledge of defence, diplomacy, and development.
On the evidence of yesterday’s Commons statement, Labour backbench opinion is broadly pro-Palestinian – so pressure on the party leadership’s line is likely to intensify during the weeks ahead.
Hard-nosed politicians and commanders, and their legal departments, might be able to mount coherent defences of the IDF. But that won’t necessarily help them in the propaganda battle.
Perhaps most importantly of all, a carefully calibrated and adaptive approach by the UK to Israel could help constrain the cycle of escalation that is all too familiar in the Middle East.