Theology is any kind of thinking about God. Atheists are theologians because thoughts about God not existing are still thoughts about God.
Job's friends wouldn't shut up about how wrong Job was and how God was punishing him. Job continued to say that he was striving to be blameless before God. In the end, God gets the last word. Job 42 says that YHWH's anger burned against Job's friends because they "have not spoken of Me what is right, as My servant Job has" [42.7, 42.8].
Job's friends had bad theology. Bad theology is a sin. This also implies that passive theology is a sin. Further, this doesn't mean every believer must be a robust academician. It means that we have to and we get to think deeply and rightly about our Father.
What a fun thing :)