Interesting article! Thanks for posting it.
It seems to me that a lot of the Germans who immigrated in that period to the US became “Free Soilers” and economic opponents to the slavery system.
They understood that the slave plantations sucked out all the air from the local economy of the black belt. (Areas where slaves, and plantations, were concentrated.) The plantations took all the best land, dominated the political leadership, actively drove out abolitionists and Free Soilers, and organized the economy to ensure its dependence upon them.
Certainly that was the case with my German relatives who settled in the Missouri-Kansas borderlands.