Great question. This conclusion is based on the things Elihu says and the context in which he says them. I know he is a beloved character by some who read this story, but there are serious problems with him.How did you derive that Elihu is "utterly wicked"???
Elihu operates essentially as a prosecutor and a persecutor to Job. For starters, look at what Elihu says in Job 34:36 "Would that Job were tried to the end, because he answers like wicked men."
Yet we know God has deemed Job as a blameless man, one who fears God and shuns evil in chapters 1 & 2. Then at the end of the story, we read in 42:7,8 that God declares that Job has spoken rightly of Him. So Elihu is wrong about his assessment of Job answering like a wicked man. Elihu's claim is false.
More dramatically, Elihu is wishing punishment on Job. He wants Job to be "tried to the end"? He's calling for Job's torture. This is sadistic.
Some consider Elihu some kind of holy counselor, but what kind of counselor who is burning with anger (as it says 4 times in chapter 32) and who wishes torture on someone would be any kind of help?
There are many points to make in answer to your question, but I'll stop here for now.