I cannot find this exact quote by Brown, it is supposed to be in the Congressional Globe for the 36th Congress.
I did find this by Brown.
http://memory.loc.gov/cgi-bin/ampage?collId=llcg&fileName=051/llcg051.db&recNum=111
Congressional Globe, 36th Congress, 1st Session, Page 34 at the end of a speech about John Brown's Raid. December 7, 1859.
"Let the conduct change; let the "irrepressible conflict" cease by your own acts; come to learn that Virginia has all the rights in the Confederacy that belong to Massachusetts; that she has as much right to have slaves as Massachussetts has not to have them, that they are equals, and exact equals in all regards; learn that principle, cherish it, and practice upon it, and you will have no occasion to sympathize with John Brown of John Sherman or John anybody else, for outrages such as that which we all protest against and deplore."
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David Upton