The U.S. Constitution actually allowed slavery to be abolished.
By having the 3 branches of government balance each other out, democracy does indeed play a prominent role in determing the laws by which we live. Fortunately, it's not the only way laws are made.
Your final statement is so completely false I find it hard to believe that you think it's true.
Britain, the 'nefarious trade' and slavery
Britain followed in the footsteps of the Portuguese in voyaging to the west coast of Africa and enslaving Africans. The British participation in what has come to be called the 'nefarious trade' was begun by Sir John Hawkins with the support and investment of Elizabeth I in 1573. (15) By fair means and foul, Britain outwitted its European rivals and became the premier trader in the enslaved from the seventeenth century onwards, and retained this position till 1807. Britain supplied enslaved African women, men and children to all European colonies in the Americas.
The 'Slave Coast' came to be dotted with European forts, their massive guns facing out to sea to warn off rival European slave traders. Each 'castle' incorporated prisons or 'barracoons' in which the enslaved women, children and men were kept, awaiting purchase by the traders, who could initially only reach the coast at those times of the year when the winds blew in the right direction. The prisons – without sanitation, with little air – must have been hell-holes in the humid coastal climates. The death rates are not known.
The trade became a very lucrative business. Bristol grew rich on it, then Liverpool. London also dealt in slaves as did some of the smaller British ports. (16) The specialised vessels were built in many British shipyards, but most were constructed in Liverpool. Laden with trade goods (guns and ammunition, rum, metal goods and cloth) they sailed to the 'Slave Coast', exchanged the goods for human beings, packed them into the vessels like sardines and sailed them across the Atlantic. On arrival, those left alive were oiled to make them look healthy and put on the auction block. Again, death rates (during the voyage) are unknown: one estimate, for the 1840s, is 25 per cent.
Plantation and mine-owners bought the Africans – and more died in the process called 'seasoning'. In the British colonies the slaves were treated as non-human: they were 'chattels', to be worked to death as it was cheaper to purchase another slave than to keep one alive. Though seen as non-human, as many of the enslaved women were raped, clearly at one level they were recognised as at least rapeable human beings. There was no opprobrium attached to rape, torture, or to beating your slaves to death. The enslaved in the British colonies had no legal rights as they were not human – they were not permitted to marry and couples and their children were often sold off separately.
Historian Paul Lovejoy has estimated that between 1701 and 1800 about 40 per cent of the approximately more than 6 million enslaved Africans were transported in British vessels. (It must be noted that this figure is believed by some to be a considerable underestimate.) Lovejoy estimated that well over 2 million more were exported between 1811 and 1867 – again, many believe the numbers were much greater. (17)
Abolition of the trade by Britain
Europeans who were Roman Catholics often treated their slaves more humanely than those of the Protestant faith, perhaps especially the members of the Church of England, which owned slaves in the West Indies. (Roman Catholics did not deny Africans their humanity and made attempts at conversion, while British slaveowners forbade church attendance.) The enslavement of Africans was justified in Britain by claiming that they were barbaric savages, without laws or religions, and, according to some 'observers' and academics, without even a language; they would acquire civilisation on the plantations.
In the 1770s, some Christians in Britain began to question this interpretation of the Bible. They began a campaign to convert the population to their perspective and to influence Parliament by forming anti-slavery associations. Slavery was declared a sin. According to some interpreters of William Wilberforce, the main abolitionist spokesperson in Parliament, it was this fear of not going to heaven that impelled him to carry on the abolitionist struggle for over 20 years. (18)
Parliamentarians and others who could read, or had the time to attend meetings, were well informed about slavery by the books published by two ex-slaves, Olaudah Equiano and Ottobah Cugoano; slightly less dramatic and emphatic anti-slavery books were published by Ignatius Sancho and Ukwasaw Groniosaw. Equiano, like Thomas Clarkson (another truly remarkable man), lectured up and down the country, and in Ireland. (19)
The Act making it illegal for Britons to participate in the trade in enslaved Africans was passed by Parliament in March 1807, after some 20 years of campaigning. Precisely why so many people signed petitions and why Parliament voted for the Act is debatable. (20) It is somewhat curious that many of the chief – including Quaker – abolitionists were importers of slave-grown produce. (21)