The Conservative party is a dangerous party. Driven by the raging cultural warriors of the right, half out of its mind with fear of Nigel Farage, it no longer conserves but destroys with as little thought for the consequences as a brattish public schoolboy trashing a restaurant.

Its threat to repeal the Human Rights Act and pull out of the European convention on human rights reveals how it has become its own negation. Conservatives flatter themselves that they defend the individual against the over-mighty state. Yet they propose to tamper with rights hundreds of millions of people recognise as their last defence against state power. Tory officials tell me and anyone else who wonders if they know what they are doing that we have no need to worry. Existing European rights will be incorporated into David Cameron’s new British bill of rights. All that will change is that English judges will no longer have to follow the rulings of the Strasbourg court.

If that’s truly the limit of Cameron’s ambition, the only question that arises is: why bother? I don’t believe it is. Even though the error-strewn statement appeared to have been scribbled on the back of the same fag packet as Cameron’s rushed announcement on “English votes for English laws”, it’s noticeable that the Tories have nothing to say about existing rights to privacy, freedom of the press and freedom of speech, family life and religious freedom. Maybe the gaps will be filled in when whichever politician who scrawled this declaration shakes off his hangover and rewrites it.

Maybe. But I doubt that the British right will allow Cameron to carry on as if nothing has changed. Those among you who don’t read the rightwing press won’t realise how irrational the hatred of human rights has become; how the right can no longer see that the European convention is about as conservative as any reputable protection of liberty can be.

Its defenders keep saying it was drafted by British lawyers determined to spare Europe from the horrors of communism and fascism. All true of David Maxwell Fyfe, a prosecutor at Nuremberg, who needed no one to tell him about the need to write a convention that would protect against totalitarianism. But Maxwell Fyfe was also a Conservative politician. When he worked on the European convention in the late 1940s, he and other European conservatives disposed of early drafts that mentioned the rights of workers. Other rights that the left regards as basic have no place in its provisions. The European convention does not mention shelter or free education and healthcare for good reasons. Maxwell Fyfe and his sponsor Winston Churchill saw the convention as a protection against the “socialism” of Clement Attlee’s 1945 Labour government as much as against the communism of Joseph Stalin’s Soviet Union, and it shows.

That today’s Conservatives can no longer support the rights their predecessors saw as conservative safeguards is a mark of their extremism. If Cameron wins the next election, that extremism will drive a majority Tory government. His supporters will not allow him to play the PR man once again and dress up our existing rights in new clothes. They will force him to abolish or restrict them. No doubt they will scream with pain when the state threatens them. But to repeat the old gag that a conservative is just a liberal who hasn’t been arrested and predict that they will change their minds is to miss the source of rightwing anger.

In a celebrated speech in 2009, the late and much missed Lord Bingham listed the liberties the European convention protects. The right not to be tortured or enslaved. The right to liberty and security of the person. The right to marry. The right to a fair trial. Freedom of thought, conscience and religion. Freedom of expression. Freedom of assembly and association.

“Which of these rights, I ask, would we wish to discard? Are any of them trivial, superfluous, unnecessary? Are any them un-British?”

Bingham failed to understand the double standards that threaten the Human Rights Act. Conservatives want rights for themselves. However, they cannot abide seeing the courts give them to groups they despise: prisoners, immigrants, Gypsies and gay people. At the root of the rage on the right is a rejection of the honourable belief in equality before the law. As they throw it away, as they give more power to a state they profess to oppose, they also abandon the sensible conservative instinct to leave well enough alone.

You don’t need to be a clairvoyant to foresee the wolfish delight with which Russia, Turkey, Hungary and other authoritarian states will greet a repeal of the Human Rights Act. They will say that if Britain no longer enforces the European convention, why should they? As of last week, Conservatives who are still capable of shame ought to be mortified that they have no rejoinder to the taunts of those who threaten an already teetering democratic order.

And a teetering Britain too. Cameron does not care that a hard-fought and hard-won campaign to keep Scotland in the union finished only last month. The Human Rights Act is written into the Scottish devolution settlement. Mess with it and nationalists would have every right to reopen the argument for independence, just as they would if the Conservatives take us out of the European Union. It is also written into the Good Friday agreement, which ended 30 years of war in Northern Ireland. This is not a document that any person with an understanding of modern history would think of changing for a moment. Cameron is happy to meddle.

In truth, he is not proposing a British bill of rights but an English bill of rights, and a Tory English bill at that. No one else would be obliged to accept it. Labour might come back into power and produce a leftwing bill of rights that included rights to union representation, shelter, health and education Maxwell Fyfe and Churchill rejected. Greens could propose environmental rights. Everyone could propose their own rights; they could change with every new parliament, all because a decent statement of minimum standards was too much for British Conservatives to bear.

The case of the Human Rights Act belies the stories Conservatives tell themselves. They call themselves individualists but want more power for the state. They call themselves unionists but threaten the union. They call themselves democrats but land more blows on the enfeebled liberal world. They boast of their common sense and call themselves pragmatists but destroy with reckless insouciance. They are a danger to themselves and everyone who votes for them.