The flow properties of concentrated suspensions having crystalline order at rest are reported. The suspensions contain charge stabilized particles and the softness of particle interaction is altered by varying the suspending phase ionic strength. The suspensions display a yield stress ${\mathrm{\ensuremath{\tau}}}_{\mathit{y}}$, and for stresses larger than ${\mathrm{\ensuremath{\tau}}}_{\mathit{y}}$, shear thin. At a critical shear stress, suspension viscosity discontinuously drops 1--3 orders of magnitude. The scaling of critical stress, yield stress, recoverable strains, and zero-frequency modulus on volume fraction and ionic strength are discussed.