It is always good sport to tweak the noses of American religious fundamentalists, particularly at election time, and you can never say they don't need tweaking, as the revelation that some of Louisiana's schools are to benefit from remarkable textbooks indicates.

Under a voucher system introduced by the state's governor Bobby Jindal – a rising star of the Republican party – pupils attending 119 schools in the state, many of them run by the religious right, will be reading textbooks which tell them that dinosaurs co-existed with humans, slaves did not have it so bad and the Ku Klux Klan had some good points. Oh, and that Mark Twain was hopeless and Emily Dickinson, who spent much of her life shut up in her house in Amherst writing poetry, was presumptuous and disrespectful – both of them because they apparently had doubts about the beneficence of the Almighty.

These are from textbooks issued over the past few years by Bob Jones University in South Carolina, a bastion of segregationism and racial discrimination for decades, until it found it might lose its charitable status. It is more than a slight irony that this has come from a governor with an ethnic Indian background, who was a Rhodes scholar not so long ago at New College, Oxford, academic home of Richard Dawkins – the prof's head must be spinning that an alumnus is sanctioning science teaching that the Earth is only 6,000 years old in schools educating some of the most disadvantaged children in the US.

Walking with dinosaurs is bad enough, but what is particularly egregious is the shameless rewriting of history that is going on in some parts of the religious right. The Tea Partiers with their tricorn hats and fifes and drums propel a mythic past of the sort many nations comfort themselves with, but the Bob Jones textbooks with their assertions that "the majority of slave holders treated their slaves well" and the KKK "tried to be a means of reform, fighting the decline in morality" are not only absurdly, demonstrably wrong-headed, but take distortion to an entirely new level. Such tropes are fading even in the South, but it is not so many years ago that an elderly white woman in Natchez, Mississippi gravely informed me that of course, in the olden days, they treated slaves well "because, after all, they were our property".

More insidious still because of their veneer of scholarship is the work of the conservative historian David Barton, who tries to wrestle the nation's history into a Christian template that it just does not fit. His latest effort, Jefferson Lies, which attempts in the face of copious evidence to the contrary, to tug the Founding Father into the evangelical Christian tradition, was last month withdrawn from publication after being described as the least credible history book in print.

The surprising thing is that the publisher Thomas Nelson, which said it had "lost confidence" in the work, did not check Barton's track record earlier for he has quite – ahem – a history of that sort of thing. It was he who seemingly discovered a document by James Madison insisting that American institutions were founded on the Ten Commandments. Unfortunately the University of Virginia, which owns Madison's papers can find the fourth president saying no such thing, ever.

An especially ingenious effort is Barton's assertion that the delegates to the Constitutional convention in 1787 solved their deadlock by praying at Benjamin Franklin's suggestion: "While neglecting God, their efforts had been characterised by frustration and selfishness… only after returning God to their deliberations were they effective in their efforts to frame a new government."

Actually, what happened was that Franklin did indeed suggest praying, but the other delegates all opposed it, not least on the grounds that there was no money to pay a chaplain. Franklin himself wrote: "The convention except for three or four persons, thought prayers unnecessary."

That does not stop pictures by zealous modern artists, showing the convention on their knees, bathed in divine light, from gracing the walls of Christian right institutions such as Patrick Henry College near Washington, which prides itself on placing its students as interns with Republican congressmen. One even made it to be an adviser to the Bush administration in Iraq.

What makes this important is precisely that such falseness informs and is taken up by the Republican right to construct an image of the US and its constitution in its own likeness. Barton's work has been praised by the likes of Newt Gingrich and Mike Huckabee and notions like his insinuate themselves into the thinking of supreme court justices such as Antonin Scalia with their interesting interpretation of the constitution based on the founders' supposed original intent. Scalia says: "I look at a text. I take my best shot at getting the fairest meaning … understanding what it meant at the time it was adopted." This has implications for the definition of what the founding fathers understood by phrases such as cruel and unusual punishment.

Perhaps we should not be surprised that Louisiana school pupils may soon be taught that the hardships of the Great Depression were exaggerated propaganda, or that the laws of mathematics are a creation of God. After all, it's only 88 years since the legislators of Tennessee decided to outlaw the state's own biology textbook because it taught the theory of evolution and they didn't want their children getting the wrong ideas.