You mãe a valid point IMVHO about modern slavery, or relatively speaking (number of slaves as a percentage of world population) would mean that slavery is not relatively as large as it was.
The point about Christians/non-Christians is a bit spurious for me. There are people of different religions and no religions. Freedom of religion is a right. Very different to venerating ex-slave traders. And having statues and roads named after them is venerating them.