17:12 - Hell Hath No Fury Like an Enraged Fool

משלי יז:יב

פָּגוֹשׁ דֹּב שַׁכּוּל בְּאִישׁ וְאַל כְּסִיל בְּאִוַּלְתּוֹ:

Mishlei 17:12

Better to for a man to confront a bear bereft of its cubs than [to confront] a fool in his foolishness.

Summary: 

A bear bereft of its cubs is in a state of instinctual, unthinking, animalistic rage; the same is true of a fool whose ego (or false sense of security) has been threatened and whose anger has been aroused. However, the fool is much more dangerous than the bear for the following reasons: 

1. The bear has a very narrow range of activity, making it relatively easy to anticipate what it might do and to take the necessary precautions; the fool, on the other hand, has a wide variety of retaliatory actions at his disposal and is willing to go to any lengths to get his revenge, making him unpredictable and difficult to guard against.
   
2. The danger level of the bear is apparent to all, whereas the fool might appear to be totally harmless, when – in truth – he is just waiting for the right moment.
   
3. No one in his right mind deludes himself into thinking that he can control an enraged bear, but when dealing with a fool, it is easy to fall prey to the illusion that one has more control than one actually has.

For these reasons (and more), one should avoid provoking fools, and steer clear of fools who have already been provoked.

Related Sources:

"חָכָם יָרֵא וְסָר מֵרָע, וּכְסִיל מִתְעַבֵּר וּבוֹטֵחַ" (משלי יב:טז)
“A wise man fears and turns away from harm, but a fool is enraged and confident” (Mishlei 12:16).

ריש לקיש אמר: כל אדם שכועס, אם חכם הוא - חכמתו מסתלקת ממנו (פסחים סב:)
Reish Lakish said: Anyone who becomes angry – if he is wise, his wisdom departs from him.