"Excessive taxation" in the eyes of beholders.
Southern Democrats worked for lower tariffs and by 1860 they were as low as ever, less than half of Andrew Jackson era "tariff of abominations".
Republicans wanted higher tariffs to protect US industries, but so long as Democrats remained united and strong they could block or minimize increases.
So the new Morrill tariff never passed until after Southern Democrats walked out of Congress.
And why did Southerners threaten in 1856 and then secede in 1861?
Was it over tariffs or any other similar matter?
No, it was over Republican threats to slavery -- that's what they said at the time.
“Excessive taxation” in the eyes of beholders.”
Correct. And I like the way the other guys said it too.
” . . . AS TO THEM shall seem most likely to effect their Safety and Happiness.” (Emphasis added.)