The 'Canonicity' of Romans 1:18-32

I was recently at UVa presenting a paper on Douglas Campbell's re-reading of Romans 1-4. It was an interdisciplinary conference (so, not all biblical scholars/theologians) and therefore the focus of the discussion was perhaps not the same as it might usually be (focusing on textual markers and the like).

One of my respondents, however, made a very interesting comment to me after the questions had ended. She asked whether adopting Campbell's reading of Romans 1-4 meant that 1:18-32 (along with the other segments of the text assigned to the Teacher) meant that we, as theologians, no longer were obliged to wrestle with the theology represented by this passage, as it is no longer 'canonical'.

This strikes me as a good question. I don't know whether the following responses might be adequate. First, some of the theological themes 'removed' by this passage (e.g. natural theology, issues concerning human sexuality) are also found elsewhere in the canon - and therefore we would still have an obligation to wrestle with them (although they would not perhaps carry the same weight).

Second (and this is a question rather than a response), how far are we obliged to consider seriously rival theologies that are presented in the Bible? For instance, should we consider whether Job's friends provide an adequate response to his predicament? Should we consider whether the Pharisees might be right that Jesus does not show proper respect for the Law? Perhaps an implication of Campbell's reading of Romans 1-4 is that Paul does want us to consider rival theologies - even if he ultimately wants us to accept his.