re: If secession was legal then what right did the North have to keep the South in the USA?

I think one of the key takeaways here is this notion that the North was fighting for some noble moral cause to stop slavery. bullshite. Most northerners viewed the slaves as subhuman just like the south.

I mean hell to this day there are some seriously nasty racists all throughout the north. Not to mention the "I'm not racist, but I don't want black people living anywhere near me" types.