I'm not sure what you consider a "reputable source." My degree is Master of Theological Studies at a Lutheran Seminary and my "resource" is the HarperCollins Study Bible NRSV that we used when I was in seminary. Just now I read the entire chapter of Revelation 11. Verse 18, which contains the line "the nations were angry" is part of a hymn that the twenty-four elders sang to worship God when the angel blew the seventh trumpet. See Verses 15-17. The hymn is Verses 17 through 18. More on this below. First let us put it all into context.
The Context: God's Throne Room & The Twenty-Four Elders
The Study Notes refer to Revelation 4:11 where God's Throne Room is described. This is where the 24 Elders are on their thrones before God when the Seventh Trumpet sounded (Chapter 11:15) and the loud voice spoke, at which the Elders fell on their faces and worshipped God (V. 16) with the above hymn (V.17).
THE NATIONS RAGED
The New International Version (NIV) says "The nations were angry." The New Revised Standard Version (NRSV) says "The nations raged." Since that is the language of my resource, I'll stick with it for this answer.
The Study Notes contain quite a bit about The nations raged.
Three Main Points from Study Notes
The Study Notes refer to:
1. Glory of God's Power in Psalms 46:6
The nations are in an uproar, the kingdoms totter;
he utters his voice, the earth melts.
"The nations are in an uproar is similar to "The nations are raging." But when God speaks, the kingdoms totter and the earth melts. This glorifies the power of God. Likewise, the Elders glorify Almighty God for his "great power" (V. 17) and for "destroying those who destroy the earth" (V. 18).
2. The Trampling of Jerusalem Motif in Rev. 11:1-2
Then I was given a measuring rod like a staff, and I was told, “Come
and measure the temple of God and the altar and those who worship
there, but do not measure the court outside the temple; leave that
out, for it is given over to the nations, and they will trample over
the holy city for forty-two months.
The trampling or subjugation of Jerusalem by the nations (i.e.
Gentiles) is a common eschatological motif.
"Eschatological motif" means that it is a literary symbol of end times. They give a number of examples, including Rev. 11.18 of this discussion. One of the other examples for the eschatological motif is Isaiah 63:18:
Your holy people took possession for a little while;
but now our adversaries have trampled down your sanctuary.
Another is Luke 21:24:
they will fall by the edge of the sword and be taken away as captives
among all nations; and Jerusalem will be trampled on by the Gentiles,
until the times of the Gentiles are fulfilled.
In the Bible, Jerusalem is the Holy Place, the sanctified refuge for God's children. Having unclean Gentiles trample Jerusalem means "the end of the world as we know it" to the biblical writers. Their safety is gone and they are at the mercy of their enemies. That is the meaning of "eschatological motif" as used in the Study Notes.
3. Nations' Assembly for Battle in Rev. 16:4
Here is the gist of Verses 12 to 16:
The sixth angel poured his bowl on the great river Euphrates, and its
water was dried up in order to prepare the way for the kings from the
east....I saw three foul spirits like frogs...who go abroad to the
kings of the whole world, to assemble them for battle on the great day
of God the Almighty....And they assembled them at the place that in
Hebrew is called Harmagedon.
The Study Notes say re Verse 14:
To assemble them for battle. The tumult and assault of the Gentiles against Israel is a common eschatological motif.
Another eschatological motif. Again, a number of examples are given but I won't copy them here. It's plain where this is going. "The nations raged in the hymn in Revelation 11:17-18 refers to the motifs of the wicked or the Gentiles raging and rebelling against God's great power and/or God's people.
That is what I believe the writer of Revelation was thinking when writing that passage. For more insight, one might further research his personal, cultural and historical situation. If you wish to apply the verse to your own faith and life situation, you may wish to consult a minister. I am not a minister. I am merely a theologian. As such, I try to figure out what the ancient writers may have been thinking and help others understand this so they can apply it to their own lives as they see fit. All the best.