The Psalmist is certain that his cause is just and those who oppose him are wicked:
I call on You; You will answer me, God; turn Your ear to me, hear what I say. (17:6)
Rise, O LORD! Go forth to meet him. Bring him down; rescue me from the wicked with Your sword … (17:13)
What is it like to be so sure of yourself? I am not. I am filled with self-doubt. Even when I know that I have a solid foundation for the path I have chosen, for the decision I have made, even when I know that I am doing the right thing, I still have doubts. As long as there is someone who takes a different path, makes a different decision, I wonder whether I should be so sure that I am right and he is wrong. Is this healthy humility, or paralyzing timidity?
Rabbinic texts, Mishnah and Talmud, record the rejected opinions because they see the potential for more than one correct answer. Talmud often goes the extra mile to explain the logic behind a position that they ultimate reject, to teach us that we can learn to appreciate an opinion with which we vigorously disagree.
There is a lot of arrogance in the words of this Psalmist. I wonder what happened to him to make him so certain that God tested him and found his cause just? What would happen to his faith in God if he were to discover that his enemies, whom he calls arrogant, are actually very nice people, and he is wrong?
The ultimate test of our faith is not what happens when we experience a Divine intervention proving that we are right, but rather what happens when we feel let down and discover that we are wrong!