As long as one atheist fails even once to perfectly adhere to the principles of rationality, it is not legitimate to host anything like the Reason Rally.
To read what some of the critics of the Reason Rally wrote, this has to have been the principle they were working on. Their criticism of the Reason Rally is that sometimes atheists do things that are unreasonable.
Of course, atheists are not always perfectly rational.
I think that many atheists give themselves far too much credit for rationality. Yet, I suspect it would be very difficult to find even one who would claim, "Every one of my beliefs is gained through a perfect application of perfect reason; none can be faulted on the charge of irrationality."
In fact, one of the facts that reason has taught us is that even the best of us cannot escape the fact that we have an imperfectly rational brain.
We do not see scientists claiming, "Because I am a trained scientist, all of my observations are free of bias." In fact, they say that even the best scientist cannot be trusted to make perfectly objective observations. This is why they invented the double-blind experiment - to separate observation from bias. Neither the doctor nor the patient knows who is getting the placebo, because if they knew, then this would contaminate their observations.
Many scientific publications demand anonymous submissions. This is because scientists cannot trust even themselves to avoid the irrationality if pre-judging a paper based on who wrote it. The quality of the paper depends on the quality of the arguments within it. Anonymity works against this prejudice.
Reason does not have the power to overcome bias, but reason can show us how to reduce its impact.
I would suspect every participant of the Reason Rally knows that we are all prone to rational faults such as confirmation bias cherry picking. None of us considers ourselves perfectly rational. The Rally was not a gathering of, "We happy few who are not subject to these faults." It was a gathering of "we who recognize these to be faults."
A Reason Rally does not require that every participant be perfectly reasonable. That would be an absurd requirement.
Reason still provides an ideal to be strived for even if we mere mortals often fall short of the ideal. Atheists may well share a human disposition for some forms of irrationality. However, at least we recognize this as a human weakness. We do not put a label on it such as 'Faith' and call it a virtue.
When I argue that some atheists commit a fallacy in presenting arguments in which they begin with premises true of "a religion" and end in conclusions about "religion", I can expect this to have some purchase among the atheists who read it. I can expect it to have a sting - because they can see clearly that such an argument is invalid. It even has a name - "hasty generalization". You can no more go from premises true of "a religion" to conclusions about "religion" than you can go from premises about "a black person" to conclusions about "black people".
Owing to our dispositions towards irrationality, one of the common maneuvers I tend to see when I point out the fallacy above is that somebody presents a self-serving definition of "religion". For example, a person might hold that "religion" is a practice where a person gets their moral code strictly from scripture.
Yet, that would be a special, private definition that few people would recognize. Some religions do not even have scripture - they exist in pre-literate societies. Other religions hold that morality is independent of their gods, and morality is something that even the gods struggle with. Even today, many people who describe themselves as having a particular religion hold that morality comes from someplace else. While they call themselves Christian or Jew or Buddhist, they are also, at the same time, a Utilitarian, Kantian, Objectivist, or Rawlsian.
Even if we limit our focus to those who claim that they get their morality from scripture, we see something else in fact. If we look at their behavior, a great many of them do not, in fact, get their morality from scripture. Instead, they assign their morality to scripture. They cite those parts of scripture that conform to their beliefs, give distorted interpretations of scripture that skirt their morality, and utterly ignore those parts of scripture that conflict with their morality.
If religion is to be defined as people who get their morality FROM scripture, then the number of religious people in the country is miniscule, and religion might not even exist at all.
My point here is not to argue the specifics of this debate. It is to point out that, in all of it, there is a respect for reason, even among those who make mistakes of reason. Perhaps I am the one making the mistakes. It is still consistent with a respect for reason.
However, one argument I DO NOT expect to hear - the distinction that identifies a main purpose of the Reason Rally - is the argument, "I know that all religion is bad as a matter of faith. Furthermore, because it is an article of faith, you must respect it. You must never try to bring reason up against it or ask me to defend it."
Among reasonable, rational agents, that answer is not available.
The objection that everybody at a Reason Rally must be a perfect practitioner of reason at all times, under all circumstances, without exception is absurd. Even reasonable people know that we cannot escape our biases, which is why they design experiments to provide some measure of protection against those biases. We know that reason is difficult, but it still is worth striving for.
It certainly works a lot better than the claim that, "I think that your life, well-being, and aspirations must be sacrificed. I hold this view without reason or evidence - as an article of faith. Because of this, you - whose life, well-being, or aspirations are to be sacrificed - must respect this and go along with the sacrifice." This is a claim that reason itself rejects.