 Complete the following phrase:  When the document was published, Northerners were outraged by what they considered a Southern attempt to extend slavery. American free-soilers, recently angered by the strengthened Fugitive Slave Law passed as part of the Compromise of 1850 and requiring officials of free states to cooperate in the return of slaves, decried as unconstitutional what Horace Greeley of the New York Tribune labeled The Manifesto of the Brigands. During the period of 