Pierce believed in the Constitutional right of a state to allow slavery but he was not pro-slavery. Therefore it seemed reasonable to let the people in a territory to decide if they wanted to allow slavery instead of the using the Missouri Compromise procedure to admitting states in pairs, one slave and one free.
However, Nebraska was anti-slavery so unless Kansas voted to be a slave state, the balance would be upset and this is what caused all the trouble in Kansas.
it hardened the opposition to slavery
No. You are confusing James Buchanan with Franklin Pierce, I think. Pierce was not a diplomat .
He believed that compromise was sometimes necessary in a republic. He was willing to look for mutual concessions in the conflicts over slavery.
Not sure what you want to know. Franklin Pierce had a rather sad life. His wife had a fragile psyche and did not want to live in Washington. All of his children died before reaching adult-hood. He had a problem with alcohol and was rather thrust into the Presidency by party bosses who planned to run the country. The nation faced many problems, the most pressing one being slavery.
Franklin pierce
slavery
Benjamin Franklin's fears are... Slavery America's Suffer
it opposed slavery.
slavery
James Ravel was a free black man who was illegally captured and forced into slavery, which was not the typical experience for slaves who were born into bondage or brought to the Americas through the transatlantic slave trade. His situation was unique in that he was fighting for his freedom from a position that was not legally recognized as slavery.
The southerners supported Franklin because they trusted him in the issue of slavery. The northerners supported Franklin because he opened a railroad to the west coast , helping revive the slavery controversy.
it opposed slavery