We all think that W. must have been the president to make the worst impression abroad in the history of these United States, but Tyler may have given him a run for his money.
In a time when the great empires of Europe, France, England and some of the German kingdoms were outlawing slavery in their territories, Tyler was sending secret agents over to the UK to promote it with propaganda and letters to the editor in British newspapers written under false names.
He actually appointed an 'ambassador' to slavery in the UK who would put a good face on the peculiar institution. While the UK was certainly not blameless for historical atrocities during the period of the mid 1800's, it can certainly take credit for the abolitionist movement that spread to the North.
Instead of heading the call of historical inevitability though, Tyler dug in and was determined to prove to his friends abroad that slavery was not only necessary, but also was righteous. He used the same pseudo science Jefferson used in his 'Notes on the State of Virginia' to try and prove his racial points.
I guess Tyler's refusal to admit that slavery's days were numbered is similar to Tea Partiers that refuse to believe pollution and global warming exist. They hold this view because it's more convenient for them if pollution doesn't exist, that way they can continue their life style unfettered by the inconveniences and moral dilemma of causing harm to their world.