Not saying your brother's theory is right, but just because something isn't a real treat doesn't mean it can't be perceived as a threat (and consequently be lobbied against)

Pulpwood is usually the worst market for wood. It takes lower quality wood than other end users, so it is an important market. But pulpwood might sell for $15 a ton while a single high grade log weighing less than a ton might sell for hundreds of dollars.

Losing the pulpwood market would mean that the cost mix would shift for other timber products but it wouldn't threaten the industry.

I'm not sure that a good, cheap process for turning hemp into paper would be that much of a threat to the pulpwood paper makers. Hemp prices can only go so low before farmers won't plant it. An awful lot of pulp wood isn't competing with corn (and any other agricultural commodity) for space to grow.

edit: Here's some global production statistics that back up paper being an important market for wood but not critical:

http://www.fao.org/forestry/statistics/80938/en/

My old man worked for DuPont for years and his theory was that they lobbied against hemp because of the competition to the then newly devolved nylon.

Here's [1] a good rundown of the conspiracy. To wit, it's a conspiracy of two: DuPont wanting to outlaw hemp which could have provided an alternative to Nylon, and Hearst which was heavily invested in wood-pulping machinery for paper production, again for which hemp was a good alternative.

1. https://www.alternet.org/story/77339/debunking_the_hemp_cons...

I have trouble with that article due to the tone. There’s no reason to refer to people as ‘potheads’ or mention Jerry Garcia with bitterness and disdain, or at all. It seems the author has an axe to grind with the remnants of 60s culture.

He isn't wrong about the Cotton folks as they see hemp as a threat. There is a slight scale difference when great plains farmers (see North Dakota in WWII) can raise a lot of crop. I think its more a unfounded fear then real, but it will probably have a year of lower profits due to novelty when legalized.