In plain words
God is beyond all attributes. Even though He may at times appear to you to be angry, it is not anger. To set devotees on the good path, He pretends to be angry when there is need. Without those very harsh words, these devotees could not change. It is nothing but acting; it is not real anger.
God has no anger or vexation of any kind. When you commit a fault, you are afraid that God might be angry. To bring your faults to your mind, He appears as though He is angry. At times, when God does not speak to you: ‘Swami must be angry with me! For some reason He is not speaking to me,’ you keep thinking. But Swami has no such thing as anger. In everything there is nothing but the principle of Prema! When He uses harsh words, you think Swami is angry. But those words too are filled with Prema! If you call, ‘Dear one! Come here,’ it sounds like a call made with Prema. If you raise your voice and say, ‘Come here!’, it sounds as though it were said in anger. This very thing gave Durvāsa a bad name in those days.
Even when He shows anger, it is only to protect the devotee!
One day Aśvatthāmā vowed that he would kill the Pāṇḍavas. Draupadī went to Kṛṣṇa and prayed to Him to save her husbands. To protect His devotees, God has to play many a drama. Kṛṣṇa went to Durvāsa, explained what had happened, and asked his help to save the Pāṇḍavas. “Dig a pit and seat the five Pāṇḍavas in it. Lay a wooden plank over it, put a chair on that plank and sit on it. Since you know the three times, the Kauravas may come to you and ask where the Pāṇḍavas are,” Kṛṣṇa was saying, when Durvāsa broke in on His words and said, “Swami! I will not tell a lie.”
Kṛṣṇa: “Satya alone is My vow. Would I, of all people, tell you to speak an untruth? Tell only Satya. But change the sound of your voice,” He said. Durvāsa agreed and did as Kṛṣṇa had said.