Earlier quoted context omitted.
I didn't suggest that there is no supportive evidence between race and drug policy, but that fact does not imply that there is a causal relationship in this case. Citing Nixon era documents to describe pre-WWI circumstances is evidence at least as poor as that which I presented.
The article itself cites in the first paragraph this much more detailed analysis of the topic, which may provide the historical context that you felt was lacking. https://www.jstor.org/stable/26391000?mag=who-took-the-cocai...
While this article confirms my assertion that whites were the majority of drug users, the drug of choice is stated to have been racially segregated (with whites preferring opiates).
Based on this, I'll accept (pending further research) that the southern bans on cocaine were racially motivated. I'd still consider the 1914 federal ban on a wider swath of drugs to be less so.