...from the .cr2 and the object file it references. I've found that editing out either by itself will result in the unwanted material assignations still loading with the figure. delete the unwanted material lines near the bottom of the .cr2 file, within the object file delete the unwanted materials by locating them after the face definitions (F lines) and coupled with the groups definitions. Materials within the .obj will be identified by "usemtl (material name)".

AFAIK the material definitions within the .cr2 simply direct poser what material qualities to apply to the material region, it's the assignations within the object file which establishes how the material regions will be grouped to the faces. Simply deleting the material definitions within the .cr2 will result in the figure loading with all the same material groups but with a default material applied.