This entire line or reasoning is a red herring..an illusion manufactured by those who to legalize pot. It's baloney. It's false. It's crap.
For a good debunking and some excellent comments: Debunking the Hemp Conspiracy Theory"
You'll see that this entire line of reasoning was pretty much invented by ONE guy and then duplicated and repeated across the internet.
It is impossible to directly prove government collusion with big business. These people are not stupid and everything is done off the record.
If you look at the fake testimony and timeline of federal prohibition against all forms of hemp, it becomes the best explanation. Why would they have experts give obvious false statements and ban hemp under the table?
Of course the other explanation is that Anslinger was such a racist that he was willing destroy the entire American hemp industry to be able to federally charge colored people.
Both explanations are equally as bad but money seems to be the more likely reason. If they wanted to attack colored people, they could have made specific laws against smoking it.
In any case, prohibition is utterly stupid since there is zero scientific evidence of any damage caused by using hemp as a drug. NOT EVEN ONE example. However, there is plenty evidence of industrial, agricultural and medical benefits.