Julian Sanchez has a very nice post about scholarly inquiry, the capacit5y to revise one's views, and public political commentary. The urge he's talking about represents an honorable part of the paradox of the public intellectual, to wit:
1) A good scholar is attracted to questions to which he or she does not yet know the answer.
2) This leads most good scholars to do something with their research other than writing elaborate justifications for the views of which they are already most certain. These views may be bedrock moral and political principles.
3) In public commentary, the scholar may:
a) comment on the areas of his or her primary expertise-- which ex hypothesi are the topics about which, at least at some point, the scholar considered the answers to be unclear, the disagreements to be interesting, the results to be interestingly nuanced and complicated-- which is likely to lead to public statements that the scholar knows to be oversimplifications or at least legitimately controversial;
b) comment on the topics about which his or her views are pretty firmly settled, which ex hypothesi aren't the topics on which the scholar has genuine professional expertise.
There are obvious easy cases. An economist doesn't have to be a specialist in rent-control to make professionally-informed public statements about its consequences; nor does he or she have to simplify or ignore ongoing debates and controversies. Those consequences are part of the well-established disciplinary knowledge of economics. A biologist needn't specialize in evolutionary biology to comment on the "only a theory" creationist claptrap. But across a wide range of subjects, I think this is a genuine problem.