I dunno...perhaps we should do exactly that so we can understand Buddhism from the perspective of a Buddhist who doesn't call their Buddhism a religion? I think that might be more informative than simply accepting the generalized consensus view of the largely uninformed 'congregation' of non-Buddhists!
My point is just that Buddhism is in general thought of as one of the world's major world religions, despite not necessarily having as a part of it what would be expected by people in Abrahamic theistic religions. Whether Buddhists would like to change that idea would be another topic. This had to do with whether "Religion" necessarily implied a belief in a God or things like that, and I believe that it does not.
I believe that our religions have always been primarily for the purpose of working on how to do the right thing, how to be a "good" person, what we should think, feel, and do in order live optimally, and that would be a basic ethical philosophy, a set of ethical principles, rules of conduct, and more specific ethical beliefs (whatever we have voluntary control over) to live optimally. Such beliefs of course vary from (sub-)culture to (sub-)culture. And that is what Humanianity is about, but with the implied culture being that of our species in general, and the recognition that there is almost no such recognized and agreed upon culture currently, with very unfortunate consequences. This is an effort to promote bringing that about more rapidly.
Which thought brings me to another concern: how to ensure that the moral consensus that will form the beliefs of humanianism doesn't end up indicating the "lowest common denominator" rather than the "highest ethical principle"?
First, I of course am curious as to why you refer to Humanianity as "humanianism." I have had the experience a number of times of people obviously changing the spelling of the word as a way of indicating some negative feeling about the concept, just as if someone referred to Christianity as "christianism." So I don't know how to interpret that misspelling, i.e., what the message, if any, is.
Regarding your basic question, though, which is a good one, I think it contains some ambiguity and/or inaccuracy regarding the nature of Humanianity. I don't believe that I have ever indicated that I expect there to be a "moral consensus." I see us as hopefully coming to increasing agreement regarding our general ethical principles. The Humanian Ultimate Ethical Principle is just a statement that it seems to me most of us want and would agree to given enough thought, though I could be wrong.
(Do you have in mind a better principle, that is as clear or clearer with regard to meaning and that would be generally agreed-upon by most people? I explained how I came to the formulation of the HUEP in Book2,
https://humanianity.com/homorationalis/hr203.html, keeping in mind that at that time I was using "REUEP" instead of "HUEP.")
If the "Belief Manual" is composed of only those beliefs (existential and ethical) that get the most votes, is there not a danger that the democratic process ultimately abandons moral excellence as a realistic target (on the grounds that for most of us it isn't a realistic target) and ends up with a grotesque compromise that is a faint parody of what was intended - the tyranny of the majority.
This is a significant misunderstanding of what the Humanian Belief Manual is, how it works, and what its purpose is. It does not consist of the beliefs that get the most votes. I contains proposed beliefs that may be different or opposite from each other. The voting is not a procedural decision-making process to arrive at an authoritarian text; it is simply a way of giving feedback as to how much agreement there currently is regarding each of the proposed beliefs, as useful information as people continue to discuss and think about the proposed beliefs. There is no requirement to "obey" the Belief Manual. It is just a tool for study.
My God I sound like a Republican but I hope you can see what I am asking here - what prevents the ethical consensus from gravitating to "dog eat dog" individualism or stifling moral collectivism? The problem I reckon is that most people don't care to be "enlightened" or "empathetic" - the latter certainly not beyond their "tribal" boundaries (but see below on that).
The Belief Manual may actually never take off and become the widely used tool that I hope it will. But if it does, it should be the stimulus for much discussion and thought, with increasingly satisfactory clarification of those principles that are most likely to be based upon accurate existential beliefs (which may change over time, of course) and upon logical consistency with the HUEP (or something like it) and those existential beliefs.
Another question - why are you defending religion and demonizing tribalism? Surely tribalism is - in reality - a more innate aspect of human nature? Surely tribalism has its positive (as well as negative) aspects? And surely it was tribalism that gave birth to religion - does it make sense to value the child but not the parent that gave birth to the child? I am not being argumentative for the sake of it - religion and tribalism are deep-seated aspects of human life - even today - and we need to be quite circumspect (I think) in how we analyze and value (or devalue) their contribution to both our current status as a species and our "shared human experience".
Yes, I agree with you. But I am not "defending religion and demonizing tribalism." There is good and bad in both. But just because something is bred deeply into us by evolution does not mean that it fosters the good life for all of us (as defined in the HUEP). Suffering promotes the survival of the species, but that does not mean that we humans cannot ethically modify such tendencies so as to have much better lives for everyone. Yes, tribalism and other tendencies within us have their positive and negative aspects. But that doesn't mean that we can't do better than the way we naturally do, through ethical modification. I recommend you read the following to get a clearer idea as to what is intended.
https://humanianity.com/humanianity/humhome.php?_menu=2#d1
I hope I have answered to some extent the complicated questions and issues you have raised, and look forward to further dialogue and resulting clarification of issues.