Feelings are not supposed to be logical. Dangerous is the man who has rationalized his emotions. (David Borenstein)

There seems to be a slight contradiction here. If feelings are not logical, then one cannot rationalise his emotions. It would only seem so. Behind all his justifications, there would lie a decision made by emotion. (Think hidden premises.)

If feelings are not supposed to be logical, and one can still rationalise his emotions, then the writer of that statement is just making a value judgement. Not very useful info.

Since I believe that people cannot rationalise their emotions into a series of purely logical self-justifying statements, I would try to see how a person who seem to have rationalised his emotions can be dangerous.

I would consider a dangerous person to be one capable of causing much more harm than the average person. Now, how would a person who seems to have rationalised his emotions be able to cause more harm than the average person?

For one who seem to have rationalised his emotions, it would mean that he has a certain theory of emotion to account for all emotions. He uses emotion to judge what he should feel, and why he is feeling the way he does. The first is an arbitrary value judgement, and the second is based on the theory he accepted, which has no guarantee of being accurate. Hmm. A theory of causation may be helpful if you could use it to do something about the effect, but in this case it is unlikely. If he follows the evolutionary approach to derive a theory of emotion, then he can't do anything about his emotions, since it is already predetermined. If he follows the biochemical approach, then the most he can do is to take drugs to change his emotions.

Okay, if you can come up with something that allows you to control how you feel, then the following parts of my argument would fall... but the thing is, you can't do anything about how you feel. While your theory of emotion can affect your emotions, ultimately you can't control your emotions when your emotion surfaces. While you can stop yourself from hitting someone in the face when you are angry, you cannot help feeling angry given the situation. Telling yourself that there is no reason to be sad doesn't help much when you are sad.

So what makes a person who seems to have rationalised his emotions different from one who has not, if both of them ultimately judge by their emotions? If there is a difference, how might this cause the one who has rationalised his emotions(I would call him "the rational" from here on) to be able to cause much more harm than one who has not("the emotional")?

Since both of them judge by their emotions, we could propose that "the rational" base his judgements on emotions that tend to lead to harm-causing actions, while "the emotional" base his judgements on emotions that cause less harmful actions. What might cause this? It seems that "the rational" may have reached a conclusion that there is nothing wrong with the harm-causing emotions and is more likely to act by judgements based on them, while "the emotional" has been taught not to feel the way that would cause him to cause harm(and has not reasoned enough to refuse these teachings), and this has an effect of him being less likely to act by judgements based on "harmful emotions". This may result in "the rational" being more dangerous than "the emotional".

However, from here on, I cannot conclude that the people who have reasoned out their emotions are dangerous even if all of the statements above are true; that would be committing the fallacy of affirming the consequent.
Indeed, if "the rational" has reasoned enough and he accepts that he should not act the way that his harmful emotions dictates him to, then a person who has rationalised his emotions may not be dangerous.

So, I don't really agree that the man who has rationalised his emotions is dangerous.