Every once in a while you may be hit with a photo that summons up strong emotions.  Admittedly, judging such an image in the context of all the others may not be an easy task. Yet, I do believe that an emotional response can be a part of the photographic experience, and may be exactly what the photographer intended.  So, let your feelings respond to the image and be a factor in your overall evaluation of the scene. 

However, there 2  issues to consider.  First, ask yourself  whether your emotional response is representative of the typical observer or a uniquely personal reaction.  Photographs producing the latter might include scenes that evoke personal tragedies in your life or faces that strongly resemble loved ones.  Such overtly personal reactions on your part can potentially bias your score, and controlling them can be a tough task.  It is a judgment call - but then, you are the judge!

Second, images that elicit anger, shock, grief, melancholy, frustration, etc., should not be scored less than images yielding good emotions, if they are of otherwise similar photographic quality!  Many well known, great photographs, such as photojournalism shots of wartime scenes, fall into the "bad emotions" category.  In the end, good or bad, emotions are emotions, and your task is not to judge the "happiness level" of the emotions produced but how well the photographer succeeds in bringing them forth from the viewer.