David -
However, my view is that the behavior they are identifying as biased is actually rational.
I don’t think that motivated reasoning implies irrationality, it merely implies a driving mechanism for how people reason in the face of controversy, how people analyze data given the implications of the resulting conclusions, etc.
It’s similar to how I view belief in Intelligent Design, or faith in god. Those beliefs, IMO, are not inherently irrational (or logical); in fact, they are entirely rational and logical contingent on certain starting premises. If you believe that a supernatural/omnipotent being exists and wants millions of children to starve to death each year, belief in ID can be logical and rational. If you believe that the bible is the word of god, then belief in god can be entirely rational and logical.
If you start with those beliefs, then any relevant data that you see can potentially be seen to confirm your belief.
I don’t understand the dichotomy you create between bias and rationality. I don’t see the two as mutually exclusive – but think of a Venn diagram of overlapping sets.