I do understand your visceral response to this (I can easily imagine similar visceral responses of my own to things that are only slightly different), but you make a leap from "the host does this thing which I am not used to" to "the host appears stark raving mad." There's a big gap there where I think you think something actually bad happened, but which you haven't articulated any negative consequences beyond your instinctive aversion.

Mmm... no, I don't think there's actually a leap here. You should understand that by "stark raving mad" I didn't actually mean anything like "I am seriously considering the possibility that my friend has had a sudden onset of severe, debilitating mental illness, and I should contact the nearest hospital forthwith". I meant something more like "my friend has suggested an activity which I find aesthetically objectionable, though I don't necessarily have any moral objections to it, and I am aware that some people out there do this and enjoy it, and that's fine. I am surprised to hear my friend suggest it, because I did not think he/she was the kind of person who enjoyed it, and am additionally surprised that he/she would think that I or any of our other friends would enjoy it, as that conflicts with what we all know about each other's personalities and preferences." As an example, if I were at a party and one of my friends said: "Hey, let's go to a strip club, and then a football game!" My reaction would be similar. I don't think there's anything morally wrong with strip clubs or football games (not inherently, anyway), but if one of my friends suggested that we go do this, I would be unpleasantly surprised, to say the least.

Of course there was also a strong element of, as you say, visceral response.

I will attempt to respond to your questions on visceral responses; I have to demur for now on negative consequences, though I will give it some thought and attempt a coherent reply soon.

Do I feel revulsion to:

Singing songs
Singing songs about things you believe strongly in
Singing or reciting things in groups

Yes (somewhat), ... (am having trouble coming up with any examples and therefore no response for now; can you provide any?), yes (strongly).

Making any deliberate effort to build group cohesion and signal tribal loyalty
Having candles
Deliberately lighting and extinguishing candles to produce an effect
Deliberately manipulating lighting to produce an emotional effect

Yes (strongly), no (unless they're scented, in which case yes, blegh), yes, yes.

Reading excerpts from authors you like
Reading excerpts from authors you respect a lot and who have shaped your worldview
Reading excerpts from only one particular author you respect (I share this concern, I'll address it in an upcoming post)

Depends on the context. Are we holding an excerpt-reading-aloud party? (Is that a thing? It should be a thing, I think. Like a poetry reading, only... reading cool stuff other people wrote aloud. I'd participate maybe.) Then no, no objection. Are we doing it because this excerpt(s) triggered an emotional response and that's what we're going for overall? Then yes, strongly object.

My objection in this case is affected by whether we're reading the thing with the intention of thinking and discussing it, in a casual atmosphere, or with the intention of not discussing it but instead just using it to generate emotions.

As for reading excerpts from only one particular author... I mean, I agree that it's a concern... but I admit that it's hard to get around the fact that Eliezer's writing is exceptionally excellent. This, however, is really not the biggest problem in the whole enterprise.

Giving a speech in deliberately manipulated lightning (taboo "sermon")
Giving a speech in to an audience whose emotional state has been deliberately altered
Giving a speech whose goal is to build group unity
Giving a speech whose goal is to call people to action towards a difficult goal

Yes, yes, yes, and... mmm... no? But something about the phrasing strikes me oddly and I can't put my finger on it...

Having some meetups featuring group activities that some portion of the potential community won't enjoy
(examples include music, as well as strategy games, presentation on material you don't care about)
Having some group activities that some portion of the potential community actively dislikes

These things don't trigger revulsion, especially not the first (one would have to be truly unreasonable to object to that!), but of course I don't like it when groups that I'm a member in have activities that I don't like. (Isn't that almost tautological?)

Deliberately provoking emotional responses (without attempting to build group cohesion or call to action)

Somewhat. I'm very wary of this sort of thing, but I don't think I find it inherently objectionable.