We should welcome new supporters of the Stop the War Coalition who have learnt that they were wrong through bitter experience.
There are times when what was bearable suddenly becomes unbearable. The war on Lebanon was one of those.
Suddenly Labour MPs, councillors and party members, who accepted and even applauded Tony Blair's dogged devotion to George Bush's foreign policy and the war on terror, could stand no more. The blockade and bombing of Lebanon, the destruction of homes, schools, roads and petrol stations, and most of all the deaths of more than 1,000 Lebanese civilians, led to calls for an immediate ceasefire.
More than 100 Labour MPs signed up for a recall of parliament, while many Labour members demonstrated and spoke out against the war. Most were highly critical of Blair - almost alone among world leaders in backing Bush's refusal to call for a ceasefire - and large numbers called for him to resign.
Many of these people had supported the wars in Afghanistan and Iraq. They had refused to speak out against the government as the occupations of these countries deteriorated and had been prepared to accept that maybe the troops should stay to finish the job. Maybe some of them still feel that way.
What made them oppose war this time? The number of deaths and the horrors weren't greater, the destruction not more widespread than in the previous wars. But somehow all the experience of those previous wars built into a wave of opposition to this one. The daily deterioration of the situation in Iraq and Afghanistan played a part, with the gradual realisation that people had been lied to when they were told things would get better.
Perhaps the greater impetus for Labour loyalists was the recognition with Lebanon that Blair was not reformable, but a serial offender. Those who believed he had secretly learnt his lesson from Iraq and would not follow Bush again were aghast.
The reaction inside the anti-war movement to this conversion of many MPs has been mixed. One response could be summed up as, "But where have you been in the past five years?"
A mass movement like the Stop the War Coalition depends on a backbone of supporters who sustain the organisation in bad and good times, who rebut government lies at every opportunity, who bring their banners on every march, who book the halls for meetings, and who rehearse the arguments about why we still oppose the war.
But every time the movement swells and grows - as it did over the summer and as it is doing around the Manchester demonstration on 23 September - it includes within its ranks those who formerly were passive or even opposed to our aims. Every meeting over the summer contained people who were new to the movement.
If they are joined by a significant number of our elected representatives - if still not enough of them - it should be a welcome development. Every MP who speaks out publicly against government policy, who is quoted in a newspaper, who comes on a Stop the War platform, brings a new voice to the anti-war movement which is likely to influence a wider range of people.
It makes the movement a genuinely mass one, something which is needed to put enough pressure to break Blair's policies and to show him the door - and that would be the most popular exit since Margaret Thatcher.
We should always remember those who fought from the beginning and who stuck with the movement all the way through - including the handful of MPs who did so. But we should also welcome new supporters who have learnt that they were wrong through bitter experience. Some of them will become the most implacable opponents of the war on terror.
After all, the way Bush and Blair's wars are going, we need all the help we can get. And what better compliment to the anti-war movement than that so many who once opposed us or had doubts now recognise we were right.
Just as with the struggles for women's suffrage and civil rights for black people, those who defend the status quo, once so confident, are now just a miserable rump - and in only five years.