Emotions are generally considered instinctive, not deliberated. You could argue that anything instinctive should be thrown out until you have a chance to verify that it serves a purpose, but brains are not usually that cooperative. Knowing you have an emotion which you do not want (I get angry when people prove that I am wrong about something which I have invested a lot of time thinking about), and being able to destroy it are two different things. If you are able to act in accordance to your best plan instead of following instincts at all times, and run error correction routines to control the damage of an unwanted emotion on your beliefs you are doing something rational.