I don't think I can give you a good reason but this website seems to do a good job of summing it up:
http://therefinersfire.org/ishmael_and_isaac.htm
Edit: This is another part of it. Start reading after the section On the Other Hand (Edit) begins. Just read the paragraph that follows the words On the Other Hand which are in bold text then stop after reading this when the sentence "Jesus' message may be love thy brother but the Old Testament has a different viewpoint." ends unless you want to read a bunch of happy, happy, joy, joy "everything is going to be alright for everyone" Christian theology.
http://wiki.answers.com/Q/What_does_Christianity_have_to_say_about_prejudice_and_discrimination
Also a look could be taken at the story of Jacob and Esau as well:
http://www.jcpa.org/dje/articles/jacob-esau.htm
Heavens to Murgatoids.
