Powell was, quite simply, the most influential politician of the post-war period. He predicted the need for the monetarist policies now followed by Gordon Brown as long ago as 1958. He predicted the British people's irreconcilability to the EU as long ago as 1969. He predicted the destruction of the United Kingdom if devolution was allowed to happen as long ago as 1974.

Oh, and he foresaw correctly that there would be terrible tensions if immigration were allowed to carry on unchecked in that famous speech - called, by a phrase he never uttered, the "Rivers of Blood" speech - in April 1968. It is for reminding the public that what Powell predicted has come to pass that Mr Hastilow is now an ex-candidate.

The insult to Powell consists in this unsustainable idea that the Birmingham speech was "racist".

There is a long tradition in the party of not reading the speech. Heath, who sacked Powell as defence spokesman, certainly had not. Nor had the two close colleagues who urged him on, his chief whip, Willie Whitelaw, and the hysterical Quintin Hogg. Oddly enough, Powell did not use the word "race" in the speech at all (this often surprises people who are convinced it is an order to the masses to vilify black people for the sole reason that they happen to be black).

He did talk about areas being changed beyond recognition and without any consultation. He did talk about inevitable tensions arising from mass immigration. He did say that immigration would work if the immigrants could be integrated into existing social mechanisms, but warned that the numbers coming were so large that integration would be impossible. Quoting Virgil, he said that if this situation were not rectified there would be trouble: "As I look ahead, I am filled with foreboding. Like the Roman, I seem to see the River Tiber foaming with much blood."

It was the sort of quotation he and Hogg used to swap at shadow cabinet meetings, during which Hogg could barely conceal his chagrin that Powell, a former professor of Greek, could always go one better. Certainly there is inflammatory language in the speech: it is Powell quoting his constituents.

The cloven hoof is shown early on, when Powell says a voter has warned him that "the black man will have the whip hand over the white man". Powell knew what he was doing. "I can already hear the chorus of execration. How dare I say such a horrible thing? How dare I stir up trouble and inflame feelings by repeating such a conversation? The answer is that I do not have the right not to do so."

There is the story of the little old lady, another constituent, whose daughter had written to Powell about her misery at living, suddenly, in the midst of an alien culture. "All I know," Powell concluded, "is that to see and not to speak would be the great betrayal."

The assault on him at the time was conducted on the basis of scaremongering. His population projections could not possibly be accurate, it was said. In fact, they understated the case. He was accused of blatant racism, even though he had merely been highlighting the danger of the racism of others.

This was a man who loved India and Indians so much that he reached interpreter standard in Urdu, and who in 1959 had made what by popular assent was one of the great speeches ever heard in the Commons, in which he attacked the government of which he was a supporter for the brutal treatment of Mau Mau detainees in Kenya. Powell was about as much of a racist as Mother Teresa of Calcutta, and his warnings in the Birmingham speech have proved grounded. So why is it such a crime for Mr Hastilow to pray him in aid? Could it be that neither the present leader of the party, nor the party chairman who sent Mr Hastilow packing, has read the speech?

I know lots of Tory MPs and peers in receipt of the Tory whip who believe Powell was right on immigration, who know he was no racist and who believe the party's greatest sin was not to take him seriously. Are they all to be sent to outer darkness, too? Will it also be a crime to point out that most of the rest of the ideology of Powellism - about money, about Europe, about the viability of the United Kingdom, about the dangers of an internationally unrestrained America - holds water just as much as this speech does?

Why is this man considered so evil that to mention him approvingly is a career-ending step, just as if someone had praised the social policies of Hitler or Pol Pot? Could it be that the jerk of the knee, and the application of no intelligence whatever, is really the driving force behind the way the Conservative Party is now run? How stupid are they?

Read the speech. Make up your own mind about whether something that told the truth then, and that tells the truth now, should 40 years later be the subject of such hysteria.

In a smug observation last week, the equality tsar Trevor Phillips congratulated David Cameron on "de-racialising" the immigration question. But who racialised it in the first place? It wasn't Powell. It was the Left, whose aim of destroying our nation state not least by destroying our culture was furthered by attacks on Powell for telling the unpalatable truth.

This surely leads us to what the Tories should say now about immigration. Instead of grandstanding attacks on the likes of Messrs Hastilow, Jenkin and Mercer, they should be turning on the people who have, by a conscious desire to allow unlimited immigration, ensured that Powell's prophecies have been fulfilled: the present Government.

We have 52 dead in attacks by Islamist fanatics in 2005 to prove how integration has failed, and what a disaster multiculturalism (now shunned by Mr Phillips) has been. Race should have no part in the immigration debate. But as Mr Cameron has realised, the numbers game should, and is at the heart of the problem.

Sadly, his determination to behave in this infantile way towards Mr Hastilow, and wilfully to misunderstand Powell even now, means that he, too, is playing his part in the great betrayal.