Can anger be acceptable?

We must forgive and be kind with everyone, including every enemy.

See the path of purification, CH. IX THE DIVINE ABIDINGS, (1) Loving-Kindness page 291.

The only one anger accepted by the Buddha is anger that keeps the practitioner goes on in the meditation. Sutta. See Tī. Ma. Sakkapañhasuttaṃ:

‘When I cultivate this kind of sadness, unskillful qualities grow, and skillful qualities decline.’ You should not cultivate that kind of sadness.

‘imaṃ kho me domanassaṃ sevato akusalā dhammā abhivaḍḍhanti, kusalā dhammā parihāyantī’ti, evarūpaṃ domanassaṃ na sevitabbaṃ.

Sutta. Ma. U. Saḷāyatanavibhaṅgasuttaṃ:

"And what are the six kinds of renunciation distress? The distress coming from the longing that arises in one who is filled with longing for the unexcelled liberations when — experiencing the inconstancy of those very forms, their change, fading, & cessation — he sees with right discernment as it actually is that all forms, past or present, are inconstant, stressful, subject to change and he is filled with this longing: 'O when will I enter & remain in the dimension that the noble ones now enter & remain in?' This is called renunciation distress. (Similarly with sounds, smells, tastes, tactile sensations, & ideas.)

P.S. The anger must feel sad.

It is not so that the Buddha rejected aversion at all. The path is not just an "increase of love" (e.g. greed), but to develop a lot of dislike and aversion in regard of what is akusala ("unskilful"), and like and desire for kusala ("skilful" -- from ku = bad, sala = cutting away -- so even the word for "good", skillful, wholesome, carries a very sharp cutting away of root).

There are times, inwardly or outwardly, where aversion is required; times, inwardly or outwardly, greed is required. For each situation it's different, and it's required to know of what is good and bad very clearly, and simply follow it.

One should not have to less aversion in regard of one's anger -- and it's suggested to kill it right, if appearing, and make its total liquidation one's foremost project: sometimes requiring aversion, sometimes greed, all however based on wisdom (but if basing on one's bias or preoccupations, for sure there will be circle-drifting, and mis-investigation of what has come into appearing).

And to have spoken here of right effort: it's good to investigate this factor more carefully. Sure, one may place improper aversion here to do so... and fools himself in both directions at the same time.

Just to get sure: there is no skillful, good, aversion which causes other being's destruction of life, depriving of their possessions, abuse, depriving of truth. As pointed out by the Buddha: neither affection (love) nor hostility can can end conflicts but are abandoned by non-hostility. Again requiring a lot of aversion to abound (abandon) and cut off non-beneficial.

(Note: Neither given for trade, exchange, other stacks, worldly gains and down-binding entertainments)

All passions including anger are to be removed but until you achieve perfection don't cut too deep, don’t remove the passion against ignorance.

Quoted below is from Shantideva's Bodhichryavatara / The Path of light. (emphasis my own)

Ah, when I vowed to deliver all beings within the hounds of space in its ten points from the Passions, I myself had not won deliverance froth the Passions. Knowing not my now measure, I spoke like a madman.. Then I will never turn back from smiting the Passions. I will grapple with them, will wrathfully make war on them all except the passion that makes for the destruction of the Passions. Though my bowels ooze out and my head fall off, I will nowise abase myself before my foes the Passions. An enemy, though driven away, may establish himself in another spot, whence he may return with gathered powers; but such is not the way of the enemy Passion. Where can this dweller in my

spirit go when I cast him out; where can he stand, to labour for my destruction? It is only that I—fool that I am—make no effort; the miserable Passions are to he overcome by the vision of wisdom. The Passions lie not in the objects of sense, nor in the sense-organs, nor between them, nor elsewhere; where do they lie? And yet they disturb the whole world

They are but a phantom. Then cast away thy heart's terror, and labour for wisdom; why shouldst thou vainly torture thyself in hell? Thus resolved, I will strive to fulfil the rule as it has been taught; how should he who needs medicine find healing, if he depart from the physician's command?

Anger is unskillful and destructive. Anger gains its power from a lack of restraint--we explode at a problem and obliterate/kill it. Strong anger leads to killing. Given that the first precept is "do not kill," angry action is Wrong Action.

Therefore if our physical work is demolition, we should exert ourselves mindfully so as not to harm ourselves or others. For example, it takes a lot of skill to demolish a house quickly, efficiently and safely. It takes skill because large forces are involved and they need to be gathered and directed with precise and calm control. Would you hire an angry or a calm construction worker?

Anger is seductive in that one thinks that "a little anger helps a bit, so maybe I can allow a little more anger. Maybe I can control this anger if I let it out just a bit." That is the delusion of anger.

When a person is angry, overcome and overwhelmed by anger, their friends and colleagues, relatives and kin avoid them from afar. --AN7.65

Even if you just slam your phone on the desk out of anger directed at no person, others will shy away from you.

“When what is incinerated do you sleep at ease?

When what is incinerated is there no sorrow?

What’s the one thing, Gotama, whose killing you approve?”

“When anger’s incinerated you sleep at ease. When anger’s incinerated there is no sorrow. O deity, anger has a poisoned root and a honey tip. The noble ones praise its killing, for when it’s incinerated there is no sorrow.”

SN1.71