Furious
Furious: full of or characterized by extreme anger; raging.
syn. crazed, enraged, vehement, wrathful

From "David Walker's Appeal":

Having traveled over a considerable portion of these United States, and having, in the course of my travels, taken the most accurate observations of things as they exist -- the result of my observations has warranted the full and unshaken conviction, that we, (colored people of these United States,) are the most degraded, wretched, and abject set of beings that ever lived since the world began; and I pray God that none like us ever may live again until time shall be no more. They tell us of the Israelites in Egypt, the Helots in Sparta, and of the Roman Slaves, which last were made up from almost every nation under heaven, whose sufferings under those ancient and heathen nations, were, in comparison with ours, under this enlightened and Christian nation, no more than a cypher -- or, in other words, those heathen nations of antiquity, had but little more among them than the name and form of slavery; while wretchedness and endless miseries were reserved, apparently in a phial, to be poured out upon, our fathers ourselves and our children, by Christian Americans!

        
David Walker, a radical free African American, is disgusted at the treatment of slaves in America.  Immediately he achieves credibility by traveling around the United States, taking detailed notes, and displaying his knowledge of history.  He concludes that blacks are the worst treated beings in human history.  He knows of “the Israelites in Egypt, the Helots in Sparta, and of the Roman Slaves,” and he still believes that African Americans are treated worse.  This enrages him to no end since because, above all, these Americans are Christians.  The Christian leaders of American are supposed to uphold the ideals of freedom and equality, yet they too degrade the blacks.  It was more understandable in the past when those in charge obviously had no intent on creating a totally free society, but to have that intent and not follow through is unacceptable to Walker.  To him it seems that all miseries and wretchedness have been reserved throughout history just so, at this time, they could be dumped on the black slaves.  David Walker became one of the most militant abolitionists, encouraging slaves to cut the throats of their masters.

“David Walker's Appeal.” 1995. Africans in America. 14 November 2004.
     <http://www.pbs.org/wgbh/aia/part4/4h2931t.html >.