I quoted that as well, maybe on this very thread. You should realize, though, that you have a major disagreement with Diogenes, who really does believe that the Confederacy would rapidly industrialize, if only they could free themselves of their commercial ties with New York City. That doesn't make much sense to me, but you guys might want to hash it out among yourselves.
Your claim that somehow Northern Democrats were just shills for the South because they happened to be in the same party as Southerners is ridiculous. Northern business interests wanted sky high protectionist tariffs to gain market share while being able to jack up prices to fatten their wallets. Both they and the working class wanted federal government handouts for corporate subsidies and infrastructure projects which would be paid by those tariffs they knew Southerners would be paying as owners of the imported manufactured goods. Many of these same corporate interests got the government to use the very same generals to commit ethnic cleansing and genocide against the Plains Indians...because those Indians were in the way of their choo choos.....
Northern businessmen never spoke with one voice. Pennsylvania iron and steel men really wanted tariffs to protect themselves from foreign competition.
New York businessmen were often involved in shipping, and those who were had no great love for tariffs. They also had no love for war with the cotton growers who gave them so much business.
New England mill owners were conflicted. Protective tariffs may have sounded like a good idea to some of them, but they got their cotton from the South and didn't want to antagonize Southern interests.
Political views cut across these categories, though. Some capitalists and industrialists were ardent abolitionists. Others had no use at all for abolition, and only wanted to keep the country together on almost any terms.
I really doubt any of these groups was the main driver of western expansion. Some capitalists, industrialists, and railroad men benefited from settling the frontier, but the main impulse for expansion was always the land hunger of agricultural interests -- very much including Southern planters.