"Śrīla Narottama dāsa Ṭhākura has sung in his prema-bhakti-candrikā, 'krodha' bhakta-dveṣi jane: anger should be used to punish a demon who is envious of devotees. Kāma, krodha, lobha, moha, mada and mātsarya—lust, anger, greed, illusion, pride and envy—all have their proper use for the Supreme Personality of Godhead and His devotee. A devotee of the Lord cannot tolerate blasphemy of the Lord or His other devotees, and the Lord also cannot tolerate blasphemy of a devotee. Thus Lord Nṛsiṁhadeva was so very angry that the great demigods like Lord Brahmā and Lord Śiva and even the goddess of fortune, who is the Lord's constant companion, could not pacify Him, even after offering prayers of glorification and praise. No one was able to pacify the Lord in His anger, but because the Lord was willing to exhibit His affection for Prahlāda Mahārāja, all the demigods and the others present before the Lord pushed Prahlāda Mahārāja forward to pacify Him."
(Śrīmad-Bhāgavatam 7.9.1, Purport)
"So Narottama dāsa Ṭhākura says that we can utilize these enemies, kāma, krodha, lobha—lust, anger, greediness. They can be utilized also for Kṛṣṇa's service. Kāma means lusty. One should be so much lusty to serve Kṛṣṇa. Just like we become lusty to have our desired object, similarly, we should be lusty to work for Kṛṣṇa as a madman: 'I must do it.' That is the utilization of lustiness. Kāma, krodha.
'Krodha' bhakta-dveṣi-jane (Prema-bhakti-candrikā). One should be very much angry upon a person who is envious of the devotees. Yes. A pure devotee, satāṁ nindā, a pure devotee who is trying to spread the holy name of God, if somebody becomes envious upon him, that person is a great offender. So another devotee should be very much angry upon such person. 'Krodha' bhakta-dveṣi-jane. Bhakta-dveṣi means one who is envious of a pure devotee. And who is a pure devotee? Who is trying to spread the holy name of the Lord all over the world. Satāṁ nindā. This is offense.
So a devotee can utilize all these elements—lustiness, anger, kāma, krodha, greediness, and moha. Illusion also can be utilized. Just like illusion... Caitanya Mahāprabhu said, śūnyāyitaṁ jagat sarvaṁ govinda-viraheṇa me (CC Antya 20.39): 'I see everything vacant, being separated from Govinda.' So when one is bewildered, illusioned, that can be also there. You become bewildered, illusioned, being separated from Govinda."
(Srila Prabhupada Lecture, Allahabad, January 15, 1971)
"One who has developed love for Viṣṇu must develop love and respect for Viṣṇu's devotees. Lord Śiva is considered the foremost personality amongst the Vaiṣṇavas. Vaiṣṇavānāṁ yathā śambhuḥ. Thus when Satī saw that her father was performing great sacrifices but had no respect for the greatest devotee, Lord Śiva, she was very angry. This is fitting; when Viṣṇu or a Vaiṣṇava is insulted, one should be angry. Lord Caitanya, who always preached nonviolence, meekness and humility, also became angry when Nityānanda was offended by Jagāi and Mādhāi, and He wanted to kill them. When Viṣṇu or a Vaiṣṇava is blasphemed or dishonored, one should be very angry. Narottama dāsa Ṭhākura said, krodha bhakta-dveṣi jane. We have anger, and that anger can be a great quality when directed against a person who is envious of the Supreme Personality of Godhead or His devotee. One should not be tolerant when a person is offensive towards Viṣṇu or a Vaiṣṇava. The anger of Satī towards her father was not objectionable, for although he was her father, he was trying to insult the greatest Vaiṣṇava. Thus Satī's anger against her father was quite applaudable."
(Śrīmad-Bhāgavatam 4.4.10, Purport)
"You have got the fighting spirit. How to utilize it? Yes. Narottama dāsa Ṭhākura recommends, krodha bhakta-dveṣī-jane: 'Those who are envious of God or God's devotee, you can utilize your anger upon them.' You can utilize. The anger you cannot give up. Our business is how to utilize it. That is Kṛṣṇa consciousness."
(Srila Prabhupada Lecture, London, August 6, 1973)