What is the significance of malcolm's army carrying branches from birnam wood to the castle?

What is the effect of the author's choice of the word loathsome rather than hateful in this sentence from the count of monte cristo? two soldiers were accordingly sent for, and the inspector descended a stairway, so foul, so humid, so dark, as to be loathsome to sight, smell, and respiration. it reveals that the unpleasant aspects of the stairway are manmade. it stresses the disgusting, offensive nature of the stairway. it suggests that the soldiers are used to the place and do not hate it. it implies that the effects of the stairway are felt only by the inspector.