It is useful to draw a distinction between beliefs and values. Rationality tells us what and how to believe, but it is silent on what and how to value. Many things that we call beliefs are actually better termed values, to illustrate their non-epistemic nature and their immunity from intellectual criticism.
For instance, I value the religious experience very highly. I value love, wisdom, and the balancing of love and wisdom. There is nothing irrational about any of these values. I can doubt whether or not the things I say I value, or the things I believe I value, are in line with what I actually value. But, I cannot doubt whether or not my values are valuable, in that there is no standard for intellectual evaluation of values.
Much of religion consists of value systems. Morality, and the teachings of compassion, wisdom, and spiritual seeking are not belief systems, but value systems. Therefore they are not subject to doubt.