alt Hacker News> or the caste system (unthinkable in Islam or Christianity, a base part of reality in Hinduism), etc.
The historical prominence of the slave trade in both the Christian and Islamic worlds should make it quite clear that it was hardly "unthinkable" but instead very rationalizable.
Rigid systems of social power hierarchy and oppression based on ancestry, perceived race, and occupation (which is a lot of what the worst part of caste is) were very much features of Christian and Islamic societies, even if their religions didn't codify them.
Right, but that proves nothing. The fact that human beings who profess religion R engage in behaviour B does not imply that B results from said profession of R. But I think you'd struggle to argue that the caste system doesn't result from Hinduism.