My interpretation was:
If their argument includes the statement that X is reasonable, that's weak Bayesian evidence against X. People don't point out that 1+1=2 is a reasonable statement; they point out that a particular candidate is the reasonable choice.
Post by fellow LW reader Razib Khan, who many here probably know from the gnxp site or perhaps from his debate with Eliezer. Somewhat related to a post we also seem to have discussed.
Edit: I linked to the wrong article! (~_~;) Fixed!