When is a Religious Belief Delusional?

[Neo-Scholastic]

OP: To you most of the religious are not delusional because their beliefs and actions comply with the belief system. When the occasional believer is identified that does not comply with the belief system (i.e. Jim Jones/extreme example, Joseph Smith/less extreme) you then consider them delusional also.

That is true. To the degree that a new doctrine or revelation is being introduced it should be viewed skeptically. That is why I admitted that the internal safe-guards include consistency with prior teachings and would add that this safeguard is more of a warning sign than a test. A new doctrine could be a further clarification of prior revelations and historically these have not always been accepted. That is why there are still religious Jews and why Christians do not convert to Islam.

Since atheists do not hold your belief system we have no choice to consider it anything other than delusion. You communicate with an invisible being (for which there is not concrete evidence) that created everything and watches over the creation all the while directing actions, proclaiming judgement's and imposing rewards/punishments.

I do not consider the practice of prayer, in and of itself, evidence of delusion. The idea that there is a level of reality deeper (or higher depending on your perspective) and more fundamental that what is currently known does not seem on its face to be irrational. After that, it is more a difference of degree than of kind by which we evaluate its reasonableness.