To someone living in 1969, the term Freedom March would probably have brought up images of the large demonstrations for civil rights that had occurred earlier in that decade.

The mention of dogs, clubs, and hoses comes directly from some of the most compelling images of the civil rights movement.  Protestors, most notably in Birmingham, Alabama, were attacked by police dogs and sprayed with extremely high-pressure water shot out of fire houses.  There were also instances, such as that of the Freedom Riders of 1963, where people were clubbed by mobs.