Appeals to emotion are almost always to be scorned, but the use of emotion to make appeals is to be admired. To stir up emotions merely to stir up emotions is the tactic of the demagogue who then uses those emotions for his own unstated purposes. Because of this, many teachers stress the need to be the perfect Mr. Spock, logical to the core, all light but no heat. But this confuses means and ends. Emotion as an end is fire raging out of control, but your argument needs to have some fire at its core in order to generate the energy to make the engine run.

Any argument worth making must have some emotion behind it. At the core, we are motivated by our irrational likes and dislikes, but the accidental contingencies of our births and upbringings. We have our likes and dislikes, our loyalties and enmities, our loves and hatreds. Together, these make us who we are. Without them, we have no personality, no individuality. You need to believe, or at least pretend to believe, your argument if you are going to convince your reader. Like an actor on a stage, you have to put some heart into your act.

Do not, therefore, be afraid to burn with enthusiasm. However, be sure that you have a strong argument constructed to contain the fire.