Correct, the OPs buyer did not want them sprayed with glyphosate.  Matt is implying that the crop must be destroyed because it is off label.  I see nothing legally prohibiting Canadian farmers from using glyphosate as a dry bean desiccant preharvest.  The OP needs to find a buyer that will accept kidney beans that were preharvest sprayed with glyphosate; since Canadian buyers have been pressuring producers to not use glyphosate this may be a difficult task and an opportunity to salvage the situation, which is what the OP is asking.

The OP is in no different situation than US dairies using rBST, which is still legal in the United States, but the majority of milk processors have quit buying rBST milk because of pressure to provide milk produced from cows that were not given rBST.  Both situations are the case of the free market dictating changes in production practices, unlike CA Prop 12 which is laws prohibiting practices that are considered safe and humane.