Yes, the desire to feel any specific mood can lead people into error. At the same time, however, some moods are symptoms of error, and others are symptoms of accuracy. When someone expresses his views with a calm mood, you consider him more reliable than when he expresses his views with an hysterical mood. We give more credence to someone who discusses alleged war crimes somberly than if he does so flippantly. As far as I can tell, this is justified.
You can learn a lot by comparing the mood reasonable proponents would hold to the mood actual proponents do hold.