1. Assume the best arguments for Atheism include one or more of the following:

a) the Argument from Evil
b) alleged defects in religious scriptures
c) alleged contradictions between divine attributes
d) negatively, the claimed absence of sufficient valid evidence for theism (where “valid” is often taken to mean “scientific”).

It is not necessary to assume that all of the above arguments are good.  (Indeed, claims (c) and (d) are in significant tension with each other, since without good evidence for any specific divine attributes, a fortiori there cannot be evidence for contradictory attributes.)  Minimally, the claim is only that if ALL of (a)-(d) fail, it is unlikely that one can reasonably be highly confident that Theism is false.

2. Note that every one of these arguments requires doing some theology to assess its validity:

(a) requires constructing a concept of “God”, and using it to make “predictions” (or really “retrodictions”) about what God would do.

(b) requires reading said Scriptures, and figuring out the best interpretation of their meaning.  Note that when deciding between 2 possible interpretations of a text, even in non-religious contexts it is usually more rational to select the interpretation with fewer defects (principle of charity).

(c) requires constructing the most plausible concept of “God”, using either natural theology (evidence from Nature) or revealed theology (evidence from putative divine revelation).

(In particular, note that no divine attribute should be added to the list without there being, at least provisionally/hypothetically, one or more reasons to think God would, if he exists, have that attribute; and the precise phrasing of the attribute should be tailored to those reasons.  Thus, the analytic philosophy habit of discussing various divine attributes apart from their contextual justifications, is fruitless and silly, because removes from the discussion any reason—apart from mere logical consistency—to accept one formulation over another.)

(d) requires understanding sufficiently what various religious people take as evidence for God, prior to assessing its validity.   And note that this is not just one type of thing, but rather a plurality of widely divergent kinds of sources of belief.  Being rationally highly confident of (d) requires showing that ALL such evidences are bad!

3. Like other intellectual endeavors, theology is a skill.  It can be done either well, or poorly.  If it is done poorly, then one might well wrongly draw out implications, that a more competent handling of the subject would not deduce.

This is for the exact same reason that e.g. a person making an “intelligent design” argument that some feature could not have evolved, would need to have some knowledge of biology and Darwinian evolution.   If they have errors in their understanding of biological evolution, this could well lead to them incorrectly identifying such features.

4. From 1-3, it follows that it is impossible for a person to reasonably be highly confident of Atheism, unless they are either:

i) good enough at theology to reasonably trust their own theological judgements, or else
ii) they believe in Atheism on the authority of some other person(s) who does meet criterion (i).

It certainly does not follow that an atheist would have to be highly interested in every aspect of theology, no matter how technical or unrelated to the epistemic justification of Theism.  The theological competence required to assess the validity of religion, is not exactly the same as the theological competence useful for a religious practitioner.  But a certain sort of genuine and deep (non-superficial) competence in the domain of religious philosophy is nonetheless required, to evaluate said arguments.

5. It is essentially impossible to become an expert at a subject, if you have contempt for everyone who does it, and you are unwilling to learn the subject in any significant detail.

It is also difficult to become good at studying theology when your main goal in studying it is to derive a contradiction, so as to refute theology.  This is because, in EVERY intellectual subject (including math, physics, biology…), progress arises by confronting apparent conflicts among truths, and then identifying a more comprenensive viewpoint which resolves the conflict.  Proceeding immediately to dismissing the entire subject, short-circuits this process in a way that makes acquiring genuine expertise impossible.

6. It is also highly unlikely for the contemptuous person described in 5 to disbelieve in religion on the basis of a good argument from authority, as such individuals are likely to select authorities on the basis of them being good at rhetorically expressing contempt, rather than on the basis of them being good at theology, as described above.

7. Nothing above rules out that there might be people who are rationally justified in being highly confident of Atheism.

However, 4-6 above show that the set of such justified atheists is going to be nearly completely disjoint, from the set of atheists who express great contempt for all religion, especially if their dismissal of religion relies heavily on rhetorically expressing such contempt.

8. One possible loophole in the above would be if the emotional reaction of contempt happens only AFTER the atheist first acquires sufficient theological expertise to become highly confident of atheism on rational grounds.  (Just as, it is not an ad hominem fallacy to insult an opponent, after providing a logical refutation on other grounds.)

However, it is highly suspicious if this contempt appears:

A) soon after a deconversion from a fundamentalist religious tradition, or
B) prior to the age of 20, or
C) in a person who has not closely studied philosophy of religion (at least as a hobbyist) for at least 1 decade.

From a sociological perspective, such contempt is more likely to be a rhetorical maneuver, designed to shore up hidden doubts, rather than a considered and expert response to the full state of the evidence.

Furthermore, even if the contempt appears later in time from the rational justification of a person’s Atheism, it will still have the psychological tendency to prevent valid theological reasoning in the future, downstream of that contempt.  Thus, as soon as the person becomes contemptuous, their degree of justification will naturally tend to corrode and decay over time, as they begin to rely on it more.

This might not be so big of a problem if their initial reasons were completely unimpeachable.  But it means they lose the benefits that might otherwise have accrued from a greater increase in maturity and understanding over time.  (One could easily imagine a scenario where that greater understanding would undermine the original arguments against religion, but the person never learns this because they are frozen in their understanding at a particular point.)

9. One could try to make a parallel argument concerning religious believers. But an important difference is that most religious epistemology makes unapologetic use of arguments from authority, parallel to (ii).  Being religious because you have faith in God, and you trust some specific religious authorities appointed by God to be doing theology well, is not IN GENERAL a self-undermining attitude, in the same way that contemptuous atheism is.  (Again, that doesn’t mean the authority is actually good, just that the attitude is not self-refuting.)

(Though there might well be parallels with respect to certain specific arguments for religion, e.g. arguments against evolution by people who don’t want to learn about evolution.)

An atheist making a general objection to religious epistemology would need to be based on circularity rather than self-defeat.  But circular arguments can often be turned into valid chains of reasoning by finding some alternative justification for one of the premises.  In particular, the theist does need some reason to believe in God’s existence that isn’t just a bare “trusting God that he exists”!  But there are many candidates for such reasons, which people who do good theology know about.

10. The atheist with contempt will probably respond to this post by making a comparison with some totally bunk subject like Astrology or Homeopathy, and trying to make the case that religion is parallel.  I don’t think this parallel works.  In order to know that Astrology or Homeopathy is bunk, you certainly do NOT need to be an expert in reading people’s charts or the exact details, but you do need to be conversant with the main ARGUMENTS for why they can’t work, which largely come down to arguments about physical causality that are widely accepted throughout the sciences by people with a wide variety of philosophical views.  The arguments are largely disconnected from the details of precisely how to use these systems (even though, in principle, a sufficiently amazing argument based on the empirical details could in principle overcome the causal details).

The arguments against religion are (if taken seriously) much more involved and subtle than this—as can easily be seen by making an even cursory effort to follow what the smartest philosophers (including professional atheist philosophers!) say about the topic.