You have a lot of detailed criticism of Christianity's relationship with black slavery, but no evidence for your claim that Islam supporting the enslavement and dehumanization of Black people. If you have any such evidence, I would like to see it. As far as I know, Islamic Slavery was not racially based. In fact, Muslim cultures enslaved at least as many white people as Black people. That’s why the word “slave” derives from the name for the Slavic white people they enslaved. Islamic law did legitimatize slavery. In fact, slavery was not abolished in Saudi Arabia until the 1960s. But Islamic law also gave rights to slaves that made Islamic slavery a much more humane institution than Christian slavery (at least in theory). I have more detailed information on this here.