I haven't got any laws to refer to, and don't know enough about this topic to make up my own opinion, but I found the information I heard interesting, and opened up a new perspective to me. Not to mistake this for being facts (again, I have very limited knowledge on this), but a perspective that tell me that there may be structural reasons for the amount of black men being incarcerated in the US.
Maybe it's something else, like a cultural such as that you've touched upon. I don't know. I'm gonna step out on a limb here, trying to recall what I saw in some documentary, but here it goes: If I'm not way off, the documentary claimed that the use of crack cocaine was more widespread in the black community than in the white. The white did other drugs, but it was the war on crack cocaine that was chosen by the government. This was during Regan. The war on drugs, or more precise, the was on drugs used primearily in the black community, led to more black men in prisons. So the war on drugs was actually a continuation of black oppression.
I my memory was not way off, I think that what you wrote is quite the same as the claims put forward in that documentary.