What does John Quincy Adams say about slavery?

Adams was particularly zealous about his abolitionist
stance.  It is interesting to note that he was more defiant and clear about his stance
on slavery than anything else during his presidency.  There was little miscommunication
about where he stood during slavery.  At the emergence of the Missouri Compromise, Adams
recognized that the issue of slavery vs. free states would tear apart the Union, as the
nation could not possess both realities in it and be called "one nation under God." 
Additionally, Adams was intense about arguing that the issue of slavery and the
proportions to which the issue had risen prior to 1860 was due, in part, to the
Constitution.  While the United States "had prohibited the international slave trade,"
it permitted it domestically under the Constitution.  Adams' implication here is that
this fundamental disconnect had to be addressed.  It was also the basis of his argument
to the Supreme Court as he argued for the slaves aboard the Amistad
slave ship that had killed the captain in order to not enter the life of
enslavement.  Adams' thoughts about slavery were unique at the time for while
politicians were either in support of it or looking to negotiate it away through popular
sovereignty or advocating states' rights, Adams' said that the issue had to be called
out as morally wrong and politically infeasible.