There was a mistake that used to be made quite frequently in evangelical circles in the 90s (they have since learned better) in the assessment of pop culture: an author can only be speaking his own thoughts in his own voice. It's a mistake because it's too simplistic: sometimes an author is speaking in his own voice, but sometimes it's the voice of a character, or--most complicated--sometimes it's a number of voices all happening at the same time.
Most songwriters rarely do the first, for the same reason so few novelists do: reality just isn't that interesting. One has to invent, combine and embellish to get the best possible results. The second is a common technique of high-brow and attempted high-brow alike: the singer could be the point-of-view character who is not necessarily the person singing (as Patti Smith did, and does, all the time), or the singer could be the narrator of a story or series of images who has no relation to the story itself (Jim Morrison, or Thom Yorke). For polyvocality, there's someone like Stuart Murdoch of Belle and Sebastian, who has started to resolve the question of identity in his lyrics by having different people sing each part.
This is also what Kanye does, and it is the single most controversial thing about his music now. When he samples vocals, they're no longer to provide a hook--they're to give another voice to throw into the mix, often three or four in the same song. As a result, critics go about making basic mistakes in their criticism, indeed, the same "if Kanye raps it it must be an exact representation of what he thinks" that evangelical audiences used to make. To wit: "Devil in a New Dress" is not a happy song. If your interpretation relies on him approving of the decision-making of the characters in said song, you've missed the point.
Which leads me to the intriguing possibility that the reason no one can make sense of "Blood on the Leaves" is because it is that rarest of things, a pop-culture song that is anti-abortion. "Strange Fruit" is the sample because black bodies are now being destroyed by people who want to spend their money on watches, or cocaine, or a big ol' pile of money rather than accept the consequences of their actions. Now, this might not be what Kanye meant, and the song might be a mess, but it's a coherent interpretation that makes more sense of the material and the sampling choices, and it relies on being able to accept that the voice of the rapper in the song may not be Kanye West. Hopefully the rest of music criticism will join us in the 21st century, rather than assuming rap to be an unsophisticated lyrical form.