The problem of motivated reasoning

The problem I am posing here is whether one side or the other of the religious debate can be accused of being more influenced by non-truth-conducive considerations than the other. Is there anything to be gained on either side by saying "you only believe that because you want to." It is my contention, going back to C. S. Lewis, is that these wish considerations pretty much cancel each other out. and nothing is to be gained by motivational speculations. We are not in a position to judge our opponents' thinking as "motivated" while our own position is free from motives.