In stride toward freedom by martin luther king jr. in lines 70-75 what assumption's does king make about the value of gaining white support?

The value you gaining the support from those of European decent is to bring the 'white to understand.' To have someone on your side from the opposite force fighting for exactly what you are fighting for really allowing a more massive display towards people of the opposition side. 

It allows them to feel as though people of their own are fighting and makes them reconsider.