We report on optically induced nucleation and expansion of stacking faults in hexagonal SiC structures. The activation energy for partial dislocation glide under optical excitation is found to reduce to 0.25 +/- 0.05 eV, which is about 2 eV lower than for pure thermal activation. From the measurements of thermal activation and below-gap excitation spectroscopy of dislocation glide, we conclude that the elementary process controlling expansion of stacking faults is kink pair nucleation aided by the phonon-kick mechanism. We propose that solitons on 30 degrees Si(g) partials with a silicon core act as deep 2.4 eV + Ev trap sites, readily providing electron-hole recombination energy to enhance the motion of dislocations. Our results suggest that this is a general mechanism of structural degradation in hexagonal SiC.