John Calvin Commentary Psalms 79:4

"We are become a reproach to our neighbors, A scoffing and derision to them that are round about us." — Psalms 79:4 (ASV)

We have been a reproach to our neighbors. Here another complaint is expressed, to stir God's mercy. The more proudly the ungodly mock and triumph over us, the more confidently we may expect that our deliverance is near, because God will not tolerate their insolence when it breaks out so audaciously, especially when it brings reproach upon his holy name, just as it is said in Isaiah:

This is the word which the Lord hath spoken concerning him: The virgin, the daughter of Zion hath despised thee and laughed thee to scorn; the daughter of Jerusalem hath shaken her head at thee. Whom hast thou reproached and blasphemed? And against whom hast thou exalted thy voice and lifted up thine eyes on high? Even against the Holy One of Israel.
(Isaiah 37:22, 23)

And certainly, their neighbors, who were partly apostates, or the degenerate children of Abraham, and partly the avowed enemies of religion, when they harassed and reproached this miserable people, did not refrain from blaspheming God. Let us, therefore, remember that the faithful do not here complain of the derision with which they were treated as individuals, but of that which they saw to be indirectly directed against God and his law. We will again find a similar complaint in the concluding part of the psalm.