“Um...yeah... and John Brown broke into the arsenal at Harper’s Ferry to fight Walmart. Uh huh, yeah that’s it.
But yes, the industrial and manufacturing North generally supported free trade. ... “
I don’t present myself as an expert. But what I have read, and been taught, supports that the real tensions of the Civil War revolved around the North’s desire for the South’s cotton crop. The South wanted the better price that England was paying. The North needed cotton to fuel their textile mills, but couldn’t match England’s price.
So, apparently the North was pro free trade, until it was their ox that was being gored. (Not unlike most free traders).
As for slavery, there were abolishonists, and some of them were violent. But the North was ready to make a deal and would have “grandfathered” slave states, with no slavery in any new state.
That’s what I was taught.
What you wrote makes sense but then it would seem that the protectionists won the war then - not the free traders.