Summary: Emotion is not to be underestimated in human decision-making, as recent US elections and Twitter's analysis of election tweets show. In the same way candidates with the strongest emotional appeals get voters attention, so do designs. Emotion is important to confront in a design, but also should be measured and used as a tool to gain deeper user engagement.
As this analysis from Twitter shows, Trump won emotion. Politically he utilized all emotion (good and bad) to attract attention to his "fix America" message. His use of emotion attracted many voters, unpredicted by US media polls. So what does this mean for your user experience?