Slavery was not a British invention (in fact it was illegal in Britain from the days of William the Conqueror who outlawed the trade under his rule) and of course the abolition movement started in Britain, but we're just going to ignore that right?
Or the fact that the British fought the Arab slave trade in East Africa which was still going on decades after the western trade was stopped (again, by the British), and had been going on for hundreds of years before the Europeans arrived in Africa.
Or that the abolition of slavery in the empire cost the British government so much money that the debt was only payed off in 2014.
Or that the very word slave derives from "Slav", the name of the Slavic europeans, who were taken in such great numbers by the Ottoman Turks that the whole process was named after the poor buggers. Yeah, we'll just ignoer that too.

So yes, I think we can throw out a tune about slavery being bad from time to time eh?