[King George III] has waged cruel war against human nature itself, violating it's most sacred rights of life & liberty in the persons of a distant people who never offended him, captivating & carrying them to slavery in another hemisphere, or to incur miserable death in their transportations thither. this piratical warfare, the opprobrium of infidel powers, is the warfare of the Christian king of Great Britain. determined to keep open a market where MEN should be bought & sold, he has prostituted his negative for suppressing every legislative attempt to prohibit or to restrain this excrable commerce and that this assemblage of horrors might want no fact of distiguished die, he is now exciting those very people to rise in arms against us, and to purchase that liberty of which he has deprived them, by murdering the people upon whom he also obtruded them; thus paying off former crimes which he urges them to commit against the lives of another.
By the way, Lincoln, too, tried to incite slaves to rebellion - even though he could have cared less about the outcome of slavery as long as the Union was preserved.
"My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union; and what I forbear, I forbear because I do not believe it would help to save the Union."
~ Abraham Lincoln
Stewart made an error, but more importantly, he fails to recognize the current state of slavery in the world. What is a slave - a person that is completely robbed of the fruits of their labor?
What does that make you - 20%, 30%, 40%, 50% slave?
Servitude is deemed OK by many as long as it supports their political objectives. A word of common sense and decency - Taking an individual's money by force to fund anything is theft, and institutionalizing such policies is the imposition of (at least partial) slavery on those that disagree.