Abraxas,
As much as your evidence is highly supportive of your theory, I believe that there other variables that need to considered.
Crack cocaine is a highly addictive and powerful stimulant that is derived from powdered cocaine using a simple conversion process. Crack emerged as a drug of abuse in the mid-1980s. It is abused because it produces an immediate high and because it is easy and inexpensive to produce--rendering it readily available and affordable.
http://www.usdoj.gov/ndic/pubs3/3978/index.htm#WhatCrack cocaine is different from powdered in that it is mixed with ammonia or baking soda which makes it a more potent drug that can be made with less powdered cocaine. So let's assume, that the reason why many blacks are incarcerated or why many blacks use crack cocaine can be for reasons of income.
The poverty rate for whites is 8.2% while the poverty rate for blacks is 24.3% in 2007.
http://www.census.gov/prod/2007pubs/p60-233.pdfWe can assume that crack cocaine usage amongst the black population can be a function of income. It would make sense that people who are poor are more likely going to use crack cocaine due to it being more inexpensive than powdered cocaine.
I am not saying that there could be some racial implications for the law, however there are many other variables that can suggest that the relationship could be caused by something other than race.
I will conclude that the reason the sentences are so high for crack cocaine is that it is a much more addictive, powerful and cheaper drug that would yield harsher deviancy during and after consumption given the income demographic that uses it.