The Crusades and the Inquisition ... Notice how every time someone wants to draw a moral equivalence between Christianity and Islam they have to go back CENTURIES! As for people justifying Jim Crow in the name of Christ, that's the first time I have heard that one; and, frankly, I would dispute it. And as for people justifying slavery in the name of Christ, two things:

1. Yes, there were those who tried to justify slavery based on part of the Bible. Their actions in doing so reveals their nominal belief in Christianity. But when real Christians brought their moral influence to bear on the slavery issue, it was in support of abolition. John Newton, William Wilberforce, Harriet Beecher Stowe are among many shining examples.

2. When westerners went over to Africa to buy slaves--yes, buy them; very few westerners actually kidnapped Africans to bring them to the West as slaves, the people they bought them from were Muslim slave traders who thought it was good business to go into Africa and captures slaves to sell.

Once again we see a contrast: While genuine Christians worked to abolish the slave trade, slavery has been a part of Islam from the beginning and continues even into the 21st century.

For further reading:

History of slavery under Muslim rule
Slavery in 21st-century Islamism
Slavery in contemporary Africa