We don't like anger. We're scared of it. And with good reason. Anger unfocused, at loose, is a plague that rides us here in the USA, a society filled with guns and impulsiveness - not an excellent combination.
The rabbis in particular have much to say about what anger tells us about a person:
The talmud tells us, (Eruvin 65b)
אמר רבי אילעאי: בשלשה דברים אדם ניכר: בכוסו, ובכיסו, ובכעסו
ואמרי ליה: אף בשחקו
Rabbi Ilai said, by three things is a person known, "Koso, kiso, ka'aso" by his cup (alcoholic drink), by his pocket (his generosity and giving of tzedakah) and by his anger. and some say: By his laughter also.
And also (Pesachim 113b),
שלשה הקדוש ברוך הוא אוהבן: מי שאינו כועס ומי שאינו משתכר, ומי שאינו מעמיד על מדותיו.
תנו רבנן: שלשה חייהן אינם חיים: הרחמנין, והרתחנין, ואניני הדעת.
Three the Holy One, blessed be He, loves: he who does not display temper, he who does not become intoxicated, and he who does not insist on his rights [does not insist upon retribution].
... Our Rabbis taught: There are three whose life is not life; the [over-] compassionate, the hot-tempered [the boiling, or effervescing], and the [too] fastidious;
And yet there is a difference between a person who is angry and an angry person.
The rabbis are right to warn us against the angry person, who is not simply unpleasant to be around, but often dangerous.
The Talmud warns:
He who rends his garments in his anger, he who breaks his vessels in his anger, and he who scatters his money in his anger, regard him as an idolater, because such are the wiles of the Tempter: Today he says to him, 'Do this'; to-morrow he tells him, 'Do that,' until he bids him, 'Go and serve idols,' and he goes and serves [them]. Rabbi Abin observed: What verse [tells us this]? “There shall be no strange god in thee; neither shalt thou worship any strange god;” Who is the strange god that resides in man himself? Say, that is the Tempter! (Talmud Bavli, Shabbat 105b)
All of us have seen, in our own lives, or in the papers, the results of the person who makes an idol out of their own impulses and nurses their grievances to an absurd end. But anger isn't a useless emotion.
Maimonides makes the interesting point:
And so, anger is…an exceptionally bad quality. It is fitting and proper that one move away from it to the opposite extreme. He should school himself not to become angry, and even about things for which it is fitting to be angry about them. If he should wish to arouse fear in his children and household…and he wants to be angry upon them in order to [motivate them] to return to the proper [path], he should present an angry front to them in order to punish them, but his mind should be inwardly calm, like one who acts as if in the hour of his wrath, but is not himself angry."
The sages said: 'All who are angry are like one who does idol worship,” and they said that all who are angry, if one is a wise man, his wisdom leaves him; if he is a prophet, his prophecy leaves him. And the [perpetually] angry, their life is not life. Therefore, he is commanded to distance himself from anger and accustom himself not to feel [any reaction], even to things which provoke [anger]. This is the good path." (Maimonides' Mishneh Torah, Laws of Character, chapter 2)*
That is, Maimonides is warning us not to allow a lack of control in one's anger. He doesn't recognise the ability to feel strongly about something without it becoming a monkey on one's back - but he does recognise that there are things for which one must act as though one feels passion for it in order to make things happen (let's put aside the particular ends he has in mind of putting the fear of God, as it were, into "his" family)
And societally, at least here in the USA, we do recognise some piece of that - the importance of passion as a motivator. Yet we don't seem to be able to separate out the selfish, self-idolizing piece that allows people to kill one another as "a crime of passion" versus the kind of anger that allows people to take risks to make justice happen - to get angry at societal wrongs, unjust laws, racism, sexism, - and act in the passion of those feelings, to repair and make holy.
Can one separate those things? Are they the same, just different by degree? Or are they a different kind of anger? If they are the same thing, then is that why our God is a "jealous" God? Are we, in that respect, made in God's image - where the holy anger and profane anger are both refletions of one emotion, which has holy and profane expression - and how, how, do we harness one without being roped to the other?
*רמב"ם הלכות דעות פרק ב
, וכן הכעס: מדה רעה היא עד למאד. וראוי לאדם שיתרחק ממנה עד הקצה האחר, וילמד עצמו שלא יכעוס, ואפילו על דבר שראוי לכעוס עליו, ואם רצה להטיל אימה על בניו ובני ביתו או על הציבור אם היה פרנס ורצה לכעוס עליהן כדי שיחזרו למוטב יראה עצמו בפניהם שהוא כועס כדי לייסרם ותהיה דעתו מיושבת בינו לבין עצמו, כאדם שהוא מדמה כועס בשעת כעסו, והוא אינו כועס. אמרו חכמים הראשונים: כל הכועס כאילו עובד עבודת כוכבים, ואמרו שכל הכועס אם חכם הוא, חכמתו מסתלקת ממנו, ואם נביא הוא, נבואתו מסתלקת ממנו, ובעלי כעס: אין חייהם חיים, לפיכך צוו להתרחק מן הכעס עד שינהיג עצמו שלא ירגיש אפילו לדברים המכעיסים וזו היא הדרך הטובה