Summary: No there are no such meanings to be derived from this verse. The verse is a prescription to the king to not succumb to arrogance and invite his ruin by provoking and dishonouring those who cannot be provoked/ dishonoured easily. Further the verse in no way intends to immunise anyone from from any sort of punishments with Manu explicitly mentioning Brahmins’ punishment in places.
(Also please keep in mind a Brahmin as a rishi and a king as those of the olden days. Do not compare with modern day caste system.)
As described in this answer, a Brahmin is a person categorised by qualities including peacefulness, tolerance, wisdom and religiousness, meaning he knows Dharma, not usually prone to anger very easily and practises religious austerities. Keep in mind these qualities for the explanation below
1. Explanation of the Context of the verse
The verse is included in the section of Manusmriti talking about the King’s treatment towards Brahmins only. It explains something special while talking about not mistreating and not taking undue advantage of Brahmins by the king.
The section of Manusmriti begins as follows:
Even when fallen in the deepest distress, the king shall not provoke the Brāhmaṇas; for if provoked, they would ruin him, along with his army and conveyances.—(9.313)
Who could prosper after injuring those who, on being provoked, would create other worlds and other guardians of the regions, and who would make the Gods cease to be Gods?—(9.315)
Verse 9.315 those who could make gods cease to be gods - Through the story of Nahusha being ousted from Indra’s position, it would be appropriate to understand this section in the context of an arrogant king who thinking himself as the ultimate authority, insults those who practise austerity. Here the above stated qualities of peacefulness and tolerance must be kept in mind.
In the story of Nahusha as found in chapter 100 of the Anushasana Parva of Mahabharata, he in his arrogance yokes Agastya to his car and Agastya expressing the qualities of a Brahmin is peaceful and tolerant of the situation.
Agastya also, though treated by Nahusha in this way, did not give way to wrath. Then, O Bharata, king Nahusha urged Agastya on with, his goad. The righteous-souled Rishi did not still give way to anger
It is when provoked by a further insult when Nahusha kicks (dishonours) Agastya, that he is cursed:
The lord of the deities, himself giving way to anger, then struck Agastya on the head with his left foot. When the Rishi was thus struck on the head, Bhrigu, who was staying within Agastya's matted locks, became incensed and cursed Nahushaof sinful soul, saying, 'Since thou hast struck with thy foot on the head of this great Rishi, do thou, therefore, fall down on the earth, transformed into a snake, O wretch of wicked understanding!'
This shows how an arrogant king like Nahusha who, through repeatedly provoking by dishonouring and injuring a Brahmin ultimately met his ruin.
Please note that the since Brahmins are supposed to be peaceful and tolerant, the king needs to do something so high in magnitude so as to aggravate their anger.
So the context of this section of Manusmriti is a prescription to a king that he must not be affected by arrogance of being the surpreme leader and must not invite his ruin by unduly taking advantage of the divinity, peace and tolerance of Brahmins.
2. Explaining the verse
Now that we have seen the context of the section being a prescription to the king to not disrespect Brahmins in his arrogance, the context for the quoted verse (Manu 9.319) would be the same.
The logic of the quoted verse is given in the previous verse of the Manusmriti itself:
Even though in the cremation-ground, the brilliant fire is not defiled, and it flourishes again when libations are poured unto it at sacrifices.—(9.318)
Similarly even though they betake themselves to all sorts of undesirable acts, yet Brāhmaṇas should be honoured in every way; for they are the greatest divinity.—(9.319)
This shows even when Brahmins undertake undesirable acts (compared to the cremation ground), yet with adequate austerities later on (libations in the fire), they get purified again.
From the story of Nahusha, anyone who practises religious austerities gets its fruits and any bad deed done thereafter doesn’t affect the person as much as a person who doesn’t practise religiousness. Though not a 100% accurate comparison, yet for example in the story of Nahusha as explained in chapter 100 of Anushasana Parva when he insulted the Brahmins and was cursed, the curse didn’t have as much effect due to practise of past religiousness:
In consequence of the various gifts that Nahusha had made, as also his penances and religious observances though hurled down on the earth, O king, he succeeded in retaining his memory.
In a similar manner as stated above the duty of a Brahmin involves practising religiousness and as such as stated by Manusmriti he would not get tainted/ defiled easily if he swerves from his path. After due prayashchitta and practice of religiousness again (pouring libations in the fire) the wrongful Brahmin (fire of cremation ground) becomes pure and divine again.
Sticking to the context above, the verse says just because the Brahmin indulges in some undesirable acts, it doesn’t befit the king to become arrogant to go and repeatedly chide him for it and thereby repeatedly dishonour him, because as stated by Manu if the Brahmin becomes pure and divine again, the king can still meet his ruin if the Brahmin is provoked (one who is not easily provoked gets provoked with repeated dishonouring by the king in his arrogance). If that Brahmin comes to the king’s house he must be treated with respect (honoured) and not kicked like how Nahusha kicked Agastya else if insulted (though not easily provoked) using his past austerities he can bring ruin upon the king.
Thus the verse is still in accordance with the prescription telling the king to be wise, humble and avoid ruin of his kingdom by unnecessarily disrespecting even those Brahmins who swerved from their path temporarily. But that in no way means punishment cannot be administered. It means after doing so, if the Brahmin meets the king or whatever he is not to dishonour him but instead behave in a respectful manner. (See point 4 below)
We need to remember that Ashwatthama met his fate by being cursed by Shri Krishna.
As per the verse of Manusmriti, you wouldn’t go finding Ashwatthama and specially riling him/ kicking him for whatever he did. In fact if Ashwatthama came to the king’s house, the king must remember that punishment has already been administered on Ashwatthama and therefore must not mistreat him. By practising regular austerities, Ashwatthama too will be purified from his sins and a wise king would avoid meeting his ruin by refraining from insulting him.
4. Does this immunise Brahmins from Punishment?
A big fat NO
Neither the father or the preceptor or the friend or the mother or the wife or the son or the priest is unpunishable for the King, when they do not keep within their duty. (8.335)
Further the nature of the punishment depends on the nature of the offence committed and not related to or based on the quoted verse. Let’s look at a few examples
- Adultery - As stated in this answer Brahmins are to be punished with tonsure and all the others are to be rendered with corporal punishment - here the simple reason is killing of a brahmin is a grave sin.
- For robbery - in this case the Brahmin is to be fined almost 8 (64/8) to 16 (128/8) times what of what a Shudra is fined. Manusmriti 8.337-338 says:
In the case of theft, the guilt of a Śūdra is eightfold, that of the Vaiśya sixteen-fold, and that of the Kṣatriya thirty-two-fold;—(337) that of the Brāhmaṇa sixty-four-fold, or fully hundred-fold, or twice sixty-four-fold; when he is cognisant of the good or bad quality of the act.—(338)
- For perjury, too the Manusmriti 8.123 explicitly mention a Brahmins being punished:
The king shall however fine and then banish the three castes giving false evidence; and the Brāhmaṇa he shall deprive of his clothes and dwelling.
As stated in the previous subheadings, the quoted verse is a prescription for the conduct of a king i.e. to be humble and not purposefully chide Brahmins and in no way immunises any wrongdoer from punishment.
Logically, if a person who knows Dharma (Brahmin) and is punished by the king rightfully without arrogance, it would not invite the ruin of the king or would not provoke the Brahmin’s wrath.
After punishment has been meted out to the Brahmin, the king is not to chide him constantly as he maybe still worthy of reverence and unnecessary chiding would invite the king’s ruin.
Thus to conclude the above verse is a prescription for the king to not succumb to arrogance, taking Nahusha as an example and not repeatedly “disrespect” even those Brahmins (who cannot be insulted and provoked easily) who have swerved from their path because owing to previous austerities or being purified by future austerities, they can ruin the king, even Ashwatthama for that matter.
However it does not mean punishment cannot be meted out to them, but after punishment the king isn’t suppose to go and find them and repeatedly dishonour them like Nahusha did.