But even Mr Blair sometimes seems not to understand how far we might have to go to combat terror. His government has condemned Israel's action in killing two leaders of Hamas. Jack Straw, the foreign secretary, has described the killings as unacceptable and counterproductive. Some Israelis might see that as Olympian detachment.
While in Northern Ireland it was not our policy to kill the organisers of violence, in the rougher world of the Middle East we are not normally so fastidious. Presumably Mr Blair does not believe that killing Saddam Hussein's two sons was unacceptable or counterproductive. They may have died in a firefight, but at the opening of the Iraq war the coalition flattened a restaurant because we thought Saddam was eating there.
Does anyone believe that we aim simply to detain Osama Bin Laden so he can help us with our inquiries? We would target him with a missile if we had a fix on his position.
Israel understands that its enemies respect only strength. To provide the best conditions for peace, Israel has to convince the Palestinian leadership that terrorism will not succeed and to eliminate all options except negotiation. In Israel's struggle to defeat terror or render it ineffective, it cannot fight by Queensberry rules. Killing those who send suicide bombers to commit mass murder disrupts the enemy. Terrorist leaders fear death more than the simple souls they bamboozle into dying on their orders.
The Western conscience, which revolted against the Iron Curtain, the Berlin Wall and apartheid in South Africa, is conditioned to abhor the forcible separation of human beings. We find the fence the Israelis are building to separate themselves from the Palestinians dreadful. It is an extreme step. But the situation is extreme and the barrier is effective. There has been only one case of a successful attack launched from Gaza since it was erected.
The fence disrupts Palestinian lives and certainly increases their anger. But it does not kill them, whereas the bombers claim many lives whenever they get through. The Israelis say that they will take it down when there is peace and that the line along which it runs has no significance for where new borders will lie. I believe them.
In the road map for peace between the Israelis and Palestinians it is not so much the destination as the route to it that is in doubt. It is agreed that the eventual settlement must produce two states, guarantees of Israeli security, special arrangements for Jerusalem and withdrawal from many Israeli settlements on land that was not Israel's before 1967. There are matters still in dispute, but what makes it so hard to reach the peace destination is the difficulty of synchronising the concessions that each side must make.
In the last meaningful negotiations in September 2000 Yasser Arafat's position was perhaps made difficult because he was offered too much too quickly by President Bill Clinton and the then Israeli prime minister, Ehud Barak, politicians in a hurry before elections. Arafat conversely needed a hard slog in to satisfy his people he had wrung difficult concessions from his enemies. Alas, soon afterwards he irresponsibly sanctioned a terrorist onslaught on Israel. That betrayal is the background to Sharon's statement on Friday that even Arafat's life might be claimed by an Israeli missile.
When the road map was last unfurled, by President George W Bush after the Iraq war, terrorists obliged both sides quickly to put it away again. That underlines the need to defeat the terrorists.
The European Union craves a role in settling the Middle East, but more for reasons of self-esteem than to be helpful. The French concept of a European common foreign policy is one defined by being different from America's. The EU, inasmuch as it speaks with one voice, therefore speaks to the PLO in a softer tone than America does (or Israel of course). That is unhelpful. The Palestinian leadership has to focus sharply on the need to engage in negotiation with Israel.
As European foreign ministers gathered in Ireland last weekend it seemed likely that anti-Americanism would as usual influence the outcome. Ministers arrived bravely denouncing the agreement between Sharon and Bush on Israel's plan for withdrawal from Gaza. The denunciation is perverse. That Israel should give up Gaza must be a vital part of any final settlement.
The wonder is that there is an Israeli prime minister willing to use his armed forces to drive Israeli voters out of their homes and send in the bulldozers. Withdrawal from Gaza is a milepost on the road map. You would not have thought so from the general indignation.
The reason that Israel is proceeding without Palestinian agreement to bring about what everyone knows must happen anyway is that there is no Palestinian leader with whom to negotiate, no figure who both opposes terror and has his people's support for peace.
As the ministers' meeting proceeded, wiser counsels prevailed. There was an almost comical panic that the Israelis and Americans would go it alone, leaving no place for the quartet that supposedly links the US to Europe, Russia and the United Nations and is charged with supervising the road map.
The meeting closed with a notably politer tone towards the US because otherwise the Americans would not agree to reconvene the quartet and Europe would be left looking ineffectual. Typically, Mr Blair reached that conclusion well ahead of his dimmer European colleagues, which is why he supported Bush and Sharon during his visit to Washington.
Despite America's setbacks in Iraq, old Europe looks weaker than ever. Intriguing, too, that just as Europe has given another demonstration of its impotence, division and latent hostility to America, Mr Blair risks his career to endorse a new European constitution. The main effect of the new European treaty will be to give the EU a minister of foreign affairs. Mr Blair secretly wants that about as much as a migraine.
If things go badly in the fight against terror in Europe, we may need to take extreme measures to defend ourselves. In Britain we hope to defeat the enemy while keeping most of our civil liberties intact. In that case the fight against terror in Iraq and Israel must succeed, because victory there will weaken the terrorists plotting against our cities.
We should therefore be wary of criticising Israel's tactics in case we merely send a message that we lack resolve.
