Hemp was never going to replace timber for paper, the amount of land required to replace the pulp from just one tree would make it impracticle and logistically impossible. It would mean replacing the land required to grow food with hemp for paper. BIO-Diesel made from peanut oil was going to be bigger than hemp-methanol and it was only about a decade after the MTA when synthetic rope made hemp rope obsolete. Don't get me wrong, there is still a use for hemp but it's not the panacea that some people claim. Should hemp, which contains virtually no THC be illegal? Of course not.
Regardless, the anti-corporation conspiracy theories just don't hold water. I've heard similar stories where it was "big-pharma" that did it to protect their new medicines but that fact is, it was just simple racism and ignorance that fueled it.
Today Marijuana use is still attached to the "hippy" stereotype which is slowly being replaced with the "stoner/pothead" stereotype image on the negative side and to some extent the "patient" image on the positive side. Unfortuantely, even the "patient" image is being eroded, slowly, by those that abuse the "medical" exemptions in many states. Everyone knows that getting a rec in California, for example, is a joke. Got a hangnail? Get a rec, headache? Get a rec. Pretend you hurt your leg, neck or back? get a rec, no real proof needed in most cases.
I just hope that we can get the Federal government to give control back to the States before those without true medical needs ruin it for those with real needs. Once the States have control, some will decriminalize, for adults, like booze. The biggest hurdle, right now, is the Federal government and some in our own community that turn-off those that we need to change their minds.
YMMV...