Scene that bugs me

I just watched this again, not the great MST version but the original movie, which is pretty good. But there's one scene that's always bugged me and it still did.
Is Harry really the slow witted hair trigger we believe he is? It's the scene where Hubbard tells him to shoot the girl. Harry very slowly goes through the motions which gives Kemp the chance to give in, which Hubbard's plan depends on. Would Harry be bright enough to figure this out, or just blast her as usual?