"self-delusion" in this context seems to be something like, 'a belief persisting in spite of contradictory evidence'; that or 'insufficient evidence'.
So yes, if someone is prematurely assenting to a belief without sufficient evidence, it would be. But I think its important to weigh this consideration which is more a point of analytic clarity.
Faith is something that is inherently irrational. 'Irrational' is not to be taken in a pejorative manner. Proper faith is held in diametric opposition with frameworks employing rationalistic standards. But faith itself does not pretend to be rational.
A good referential here is Kierkegaard.
If you are working within a framework that demands "evidence" and computational methods involving probabilities, a movement of 'faith' will inherently be unsatisfactory, but simply because you are asking it to interact or reconcile itself with systemic features that are entirely exclusive from it.
Now, what you may mean to ask is whether it's bad to assent to a belief in spite of insufficient evidence. ORdinarily, I'd say yes again. But there is much more to be said about it. The question soon arises, what is the benchmark of sufficiency? Pragmatically speaking, it would be easy here just to say whatever is most compelling or persuasive. But this again is not 'faith'. 'Faith' does not make persuasive cases. Persuasion is a function of rationality and as such should be kept to its camp.
Any irrational-based beliefs (faith) would naturally be distressing to someone that subscribes to a purely rationalistic program. All atheistic systems, it would at least appear to me, are purely rationalistic in basis. Granted, faith-based beliefs are irrational, they are just really bad to the rationalist, or more pointedly here, the atheist. As far as the name calling. Well, people are...
The word 'rationally', is clearly being used in different ways between us. I'm using it to describe a system that strictly employs empirical evidence, deductive&inductive support and calculation, at broad. That is, systems based here, both good and bad. Not that I personally want to address the tenability of an atheistic thesis.
The best I can make out, you, Meleager, are using "rationally" to describe something more similar to 'persuasive' or 'compelling'.
But I don't think this is a revealing way to use the word. Especially if you're calling systems that are designed as famously rationalist projects, as irrational. If you take 'rational' in the first sense that I was initially using, this clearly would not be accurate.
You had said that Universal claims are not tenable. Which, if you mean much in the same way that the Pyrrhonian cautions the Academic, I'd say certainly that's a good consideration. But if indeed this is what you mean, it is difficult to apply this critique to the rationalist. Withholding assent to all propositions does not allow the rationalist to function. Hume encountered this problem with his discussion on Testimony in his Treaties (or Enquiry- I can't remember exactly)*. That said, I think that a 'hard atheist' could very well hold a universal claim iff that claim is understood by that agent as being the most persuasive case. Not to say that the agent is saying that that proposition is in fact, extensively true.
(*)The rationalist cannot afford himself those epistemic concerns branching from the problem of induction. It is those very inductive inferences that allows a rationalist the capacity to be, well, rational. That said, I don't think that a person embarking on a rationalistic enterprise would be very successful if they didn't allow for the uniformity of experience and governing laws.
As far as the evidentiary support for or against the existence of God. I don't really care to address that here. While arguments developed by Saint Augustine and his latter Saint Aquinas provide compelling cases for a God, there are still many problems for the 'AAA' God that we find at the heart of most contemporary, monotheistic systems.
These are all things that are perhaps best addressed in a different thread.
Axiomatic or Universal propositions speaking to the nature of all of some class in all realities (notated “∀ x”) cannot be evidentiary supported neither in the affirmative nor the negative. On the other hand, extensive propositions (notated “∃ x”) detail that there is in existence, at least one of a certain class that shares such and such characteristic, and can be borne out.
Asking if God exists it traditionally is understood as making an ∀ proposition. The truth-value of which cannot admittedly be assessed. This is the proposition claiming that nowhere, in no reality does a God exist. But it is not necessary that we make an ∀ proposition regarding God’s existence.
We can contrast this against the ∃ proposition you used offered: ‘frogs exist’. There is evidential support to this extensive claim in this reality. But if you were to transmute this into an ∀ proposition, it would not hold. This is because we can imagine at least one world in which frogs do not exist. Therefore, the truth-value of proposition “∀ x: frogs exist” is indeterminable.
But this is not what your example reflected, so we are to assume that you are discussing about existential propositions. Inasmuch, we would hold any proposition to the same existential standard.
Someone can very well say though that God doesn’t exist in this reality. “∃ x: God does not exist”. This claim is completely tenable granted that there is not observable factual evidence that contradicts it. Evidence that the atheist at least would certainly maintain, we do not have.
Returning, faith does not have evidence. Faith is proof-less. A belief that has no proof, for someone that is only assessing things in terms of evidence, will obviously not appreciate said belief.
Kierkegaard does not talk about self-delusion in the way it has been discussed here. Moreover, he would not believe that you are talking about true 'faith' at all, at least in the manner it has been used here. If you're looking for where he delineates the principles features of his view on 'faith', I would read his Fear and Trembling.
Much of his discussion chastises the modern impressions of what faith is. His project is not reconciling faith with rationalistic expectation, but show how faith can be tool for procuring a contented subjective experience in one’s lifetime. But Kierkegaard is an Existentialistic writer, so this project would certainly be analytically presumed of him in some degree.
If you are considering faith as delusion, I’m afraid you have already chosen sides. The faithful, that is, those that embrace what Kierkegaard calls faith, never admit delusion into their considerations. It is simply not useful for what faith purposes to accomplish. The rationalist and the faithful purpose diametrically opposed programs.
The faithful intend to give their subjective experience meaning by become content with it.
The rational intend on understanding in some degree the objective state of their experience.