I really don't see why anyone would vote for Adams because of slavery. Adams' campaign had nothing to do with slavery and he took no actions against it as President.
Because it's 2014, and people on Atlas assume that if a party prior to the Civil War was largely based in the North that it was the 'anti-slavery' party, ignoring the fact that northern businessmen
profited from slavery and only dispensed with it when it became fully clear that the expansion of slavery meant the extinction of a free labor economy and would retard the growth of their industries.