The poet saw how the Edomites betrayed the people of Judah, so he calls on God to judge Edom. The long conflict between Edom and Judah reached its worst point near the end of Judah’s history. At that time, the Edomites handed the Judeans over to the Babylonians (Obadiah 1:10–11) and celebrated Jerusalem's fall.
This prayer asking God to bring justice uses strong language and can be shocking.