You are correct that the last 50 years or so, the violence has been mostly one-sided, but before that, you can’t seriously believe that organized white mob violence were “scattered incidents”, can you?
Here is some more information about the widespread racial violence that white Americans participated in:
“Although lynchings were decreasing slightly by the turn of the century, race riots were perceptibly on the increase. Large-scale interracial violence became almost epidemic, as increasing numbers of Blacks migrated to Northern cities. The greatest number of race riots occurred during and just after World War I. During this period the North was concerned with the tremendous migration of Blacks from the South, and the displacement of some whites by Blacks in jobs and residences, which escalated social tensions between the races. The South was concerned about the possible demands of returning Negro soldiers, who were unwilling to slip quietly back into second class citizenship.
The summer of 1919, called “The Red Summer” by James Weldon Johnson, ushered in the greatest period of interracial violence the nation had ever witnessed. During that summer there were twenty-six race riots in such cities as Chicago, Illinois; Washington, D.C.; Elaine, Arkansas; Charleston, South Carolina; Knoxville and Nashville, Tennessee; Longview, Texas; and Omaha, Nebraska. More than one hundred Blacks were killed in these riots, and thousands were wounded and left homeless.
The seven most serious race riots were those which occurred in Wilmington, N. C. (1898), Atlanta, Ga. (1906), Springfield, Ill. (1908), East St. Louis) Ill. (1917), Chicago, Ill. (1919), Tulsa, Okla. (1921) and Detroit, Mich. (1943).”
from: http://www.yale.edu/ynhti/curriculum/units/1979/2/79.02.04.x.html#c
26 race riots in a single summer. That doesn’t sound like “scattered incidents” to me.