Not a great argument, breh. You're right, Christians were horrible, too, but we shouldn't try and justify maltreatment by saying others did it, too.
The problem with religion is that it rarely helps truly eradicate racism unless it is taken up and transformed fundamentally by a group of people, as with Black Theology, Black Islam, etc. But in its original form, it rarely does, and is often predisposed towards the group of people with which it originates. On the occasion that it does eradicate some prejudice, it's usually contingent on the would-be victims of prejudice joining the religion before getting treated better.
what are we talking about here? what part of the muslim religion itself is racist? (i guess the slavery part is a problem in effect cause the way it works out is that mostly africans get enslaved..) but there's no actual theological distinctions