In a public speech, Joseph Smith calls Orson Pratt's wife, Sarah, -A whore from her mother's breast- (The Sangamo Journal. July 29, 1842). This entry is from an anti-mormon newspaper, and is the only source of this statement, however one must question whether all sources are lies simply because they are not in favor of mormonism. On the same day:
Sarah had accused Smith of proposing plural marriage to her while her husband, Orson, was away on a mission
Orson Pratt writes a -suicide' note: -I am a ruined man! My future prospects are blasted! The testimony upon both sides seems to be equal: The one in direct contradiction to the other . . .-
Regardless of whether he said the exact words -Whore- and -Mother's breast-, it is clear that Joseph pushed in a way that lead Orson to be very distraught over the situation of his wife claiming that Joseph had proposed to her, and refusing to accept that it was Bennett who had, instead.
[Source: Joseph Smith, Orson and Sarah Pratt- A timeline, http://www.exploringmormonism.com/joseph-smith-orson-and-sarah-pratt-a-timeline/]