Doesn't that make it all the more impressive? That they were a leader in abolishing something they were profiting from?
These peoples all contributed a lot of the world, and were all avid practitioners of slavery, as well as their own "racial and religious superiority".
Ideas, no, ideals, yes. Obsession over Greek and Roman civilizations held back the course of science, philosophy and ethics for centuries.
We can take the ideas of a few brilliant men for what they were while still consigning those empires to the rubbish heap of history where they belong. The world is better off for having the opportunity to move beyond the influence of those cultures.
And as an American, I would include my own country as well. You could list any number of benefits the United States has brought to humanity, in practically any field. But the world will still be better off when the US is no longer a superpower using overwhelming violence to reinforce its military and cultural hegemony.
Good riddance to all empires and superpowers.
>Can you name a major civilisation that was not trading, holding or capturing slaves during the time period the British empire was selling slaves to your country?
No. But I would describe them in similar terms. We shouldn't mourn the passing of any empire, we should move beyond the premise that any country has any right to subjugate or plunder another out of a belief in their own racial and religious superiority. Whatever good the British Empire might have brought to the world, it often did while standing on the backs of cultures it considered beneath it.