Emotions are a very human thing. They are responsible for making us feel all sorts of things in life. Their existence is not a bad thing; however, bad management of emotions is. When it comes to placing your trust in what a person says, emotion plays a big role in how that person's words will affect you and your beliefs. Of course, people have found that appealing to one's emotions is an incredibly effective tool to get people to believe them. This is usually innocuous, but can have dangerous implications if the wrong person pulls the emotional strings of a large group of people. There are several ways this can be done, although the most common way I have observed is by providing validation to a beliefs people already have and are emotionally invested in. This is a handy mechanism to sidestep reasoning since the satisfaction felt from that validation will often suppress any urge to thoroughly think through what is being said.
One common example of people using emotions like this is often found in political media. When a politician or media figure wants to provoke a certain reaction from their audience, they can throw in certain words again and again into what they say to elicit the emotional response they want. This can be done by using words that have a negative connotation with their supporters through continued association with things the target audience does not like.