It seems to me that he has a certain point, however, there is more to the rationality of a belief then the agents willingness to be open to a critical evaluation and potentially change his belief. It seems that more importantly a belief is rational when it is based upon valid reasoning, or, we could say, when it is logical. It also seems to me that a belief that is true is rational in the sense that it is rational to believe it, even if one did not arrive at that belief through a process of reasoning.
We need to make sure that when we say that we belief X (X is a place holder that is used to refer to any proposition) that we have a reason to believe X. In other words, we need to make sure that our beliefs are rational. This is what Peter says in 1 Peter 3:15 "But in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect." We need to make sure that it is rational to believe what we believe, and that our beliefs are rational.