I don't know if this is recent revisionism, but some allege that the KKK is a Christian terrorist organization. Further, from what i've gathered, mainly but probably not exclusively in the U.S. parts of the Christian religion were I think used to justify anti-miscegenation laws and the inferiority of certain races.
I've found scattered of evidence of this, like black people being considered the 'children of Ham' or something. It's not been clear.
Of course the Christian has also been, and perhaps is among the first, basis for interracial and international fraternity, in the beginning it was the only basis for unity among the 30 or 40 nations of the Roman Empire as it was one of the first mass religions. I don't see a reason to debate whether Christianity is a source of unity or divisiveness, it's a source for both, but apparently parts of the bible were used to justify the division of races; just as some are used to persecute homosexuals, and I'd like to know which ones if you know them.
edit: Further, in the show Boardwalk Empire Narcisse, who is a black Christian fundamentalist gangster and leader of the Negro Improvement Association, wipes his hand with a cloth after shaking hands with Arnold Rothstein, a Jew. I'd like to understand why he did that?
You're absolutely right that Genesis 9:20-27 (the passage about the curse of Ham) is a key argument for racists. It's been interpreted to mean that Ham and his descendants became a difference race, and that God willed them to be inferior to Shem and Japheth's descendants. Genesis 9:25 is especially explicit about this, specifically saying that Ham's descendants are destined to be slaves. Matthew 15:21-28 (the story of the Canaanite woman) also reinforces this idea of inferiority of some races with Jesus calling Canaanites "dogs." Interestingly, Galatians 3:28 was also cited, based on the idea that, while in salvation there may be no difference, on Earth, there certainly was.
Even though it's tangential to your question, this site has a speech by Bob Jones outlining the Biblical basis of segregation. It's an interesting read.
Growing up I had elderly southern relatives who would cite the story of Ham in their justifications for segregation and the supposed inferiority of non-white people.
Ham is cursed for his transgression, "marked," cast out, and his descendents said to be destined to be inferior and slaves to the descendents of his brothers'. This "mark" was interpreted by American pro-slavery/pro-segregation/etc racists as dark skin. They concluded that therefor having dark skin was a sign of inherent intellectual and moral inferiority, and that darker people were destined by God to serve the "pure" white race.
Then there are all the various passages that take it for granted that slavery was just a fact of life, and those which command slaves to obey and respect their masters. Granted, those passages were referring to ancient Mediterranean slavery that had a lot of differences from the American slave trade, but it was easy enough to use them to justify the latter anyway.
There were also a lot of religious arguments that weren't actually based in scripture at all. E.g., a quote from the judge who convicted Mildred and Richard Loving on charges of "miscegenation," in the case that eventually led to the Supreme Court striking down such laws:
"Almighty God created the races white, black, yellow, malay and red, and he placed them on separate continents. And but for the interference with his arrangement there would be no cause for such marriages. The fact that he separated the races shows that he did not intend for the races to mix."
This has nothing to do with scripture at all, but it was commonly believed for a very long time.