Jeff at Where'd That Bug Go has managed to find an alternative definition of "Spear-Chucker" that seems more likely to be the meaning of a B.C. Interior politician like Stockwell Day:
3. One who throws spears made of wood at nearby wildlife or in some cases livestock. Usually of native descent.
So Stockwell was actually comparing Easterners to primitive Indians, not dumb Black males, as I first suspected. I apologize for the error
Unless of course Stockwell is secretly a genius of rhetoric who was attempting to slag off two different races in a single remark. (Three races, if you count Easterners)