I think there is a temptation to think too hard here. Is there any work environment which remains equally functional as staff become increasingly entangled in personal relations with one another? Perhaps the current trend in the West to taboo workplace relationships has gone too far but there is a reason it started. I think your points here are interesting and could be true, but even if they were not you'd still have the effect of just having more intense relationships to navigate because employees can have more SOs on average. NB I have no experience or expertise; this is purely armchair sociology.
I think your conclusion is right but the mechanism is different.
"offending a whole polycule" isn't really a thing. Lots of people don't care about their partners' partners' opinions, and care a great deal about their friends' opinions. So poly is a wash here (although the part where a bad impression on one person can spread is real).
I think the place where poly really matters is that it means there's never an end to hitting on people. A friend who went from poly to mono says one of the best parts is how much it simplifies his relationship with women- they don't have to worry he's hitting on them, he doesn't have to worry they'll think he's hitting on them or how his actions affect will affect the success of hitting on them. (Some) poly people never get to that stage, and even for poly-saturated people it's not as absent as it is for the monogamous.
A friend and I have joked that the rule should be you only get to have one partner within EA/rationality but can have additional partners outside it, to balance "romance is an important human drive and this community is by far the best place for me to fulfill it" with "me dating within this community is costly to it".
[note: I do not consider myself part of EA, I don't follow the forum, I do have friends in the Bay Area, but they're mostly in the less-zany parts of tech. This is outside view. ]
I have a few reactions to this question.
I think my primary modeling difference from this question is that I think polyamory is just an added weirdness to the "contrarian cluster" that is bay-area-style community EA. It's going to be cult-like and unpleasant because of the cluster, and the belief that THAT particular cluster is of world importance, regardless of whether poly is part of it or not.
Given the way you wrote this, it sounds like you're using the word "polycule" to mean something like "a group of people who are all dating all of each other." I've recently heard a few people use the word "polycule" as if this is the definition.
But, uh, I've been polyamorous for 8 years, and I've literally never heard of this happening. The closest thing I've seen is a triad, in which a group of three people are all dating each other, but that's quite rare and often isn't very stable. (Newly-nonmonogamous married couples sometimes explicitly seek out a bisexual woman to date both of them, but this almost never works out. This behavior is referred to as "unicorn hunting," and it's generally frowned upon within the polyamorous community.)
"Polycule" refers to a network of one-on-one polyamorous relationships. (It's a play on "molecule" -- when you draw these graphs, they look kind of like molecules.)
For example: Alice is married to Bob; Bob is dating Carol; Carol is dating David; David is dating Edward; Carol is married to Francis. In that example, Alice *might* have a relationship with Carol, depending on how close she likes to be with her partners' partners, and depending on how serious the relationship between Bob and Carol is. But she likely has zero relationship with David, Edward, or Francis.
A "polycule" is more of a fun little diagram, and less of an actual social entity. When my "polycule" technically splits in half because I break up with a partner, there are often no substantial consequences to my life besides the change in my relationship with that one person. "Joining a polycule" just means starting to date an individual person who happens to be dating other people -- it doesn't somehow give you political power by being connected to everyone else in the polycule.
In many cases, the monogamous equivalent of "someone in my polycule is joining my team at work" would be something like "my wife's friend's tennis partner is joining my team at work." (Especially because many polyamorous relationships are pretty casual.)
My experience is that it is like having extra in laws, who you may or may not like, but have to sort of get along with occasionally.
I don't think most people actually talk very much with their in laws, or assume that people who the in law dislikes should be disliked.
I do think the effect spreading through the network is more intense/disruptive in a polykule vs in laws, but that does not necessarily determine whether the effect will work against the complaining employee. E.g. if my fictional metamour were to start a massive dramatic crisis with an employee, and put pressure on my partner to back them in it, and this left my partner confused and distressed while around me, I can very much imagine myself not backing the metamour, but recommending that my partner draws a boundary so they do not melt down in my living room, and that we both withdraw as entangled and recommend a neutral person to evaluate.
It is generally the case that as a small org grows (and grows up) workplace problems grow with it, and so HR eventually develops clear policies of what is and is not allowed. If you catch an org in its awkward teen phase, then the problems can already be significant, but the rules are not yet adopted. Polyamory as a non-conventional arrangement breaks a number of Chesterton-Schelling fences, with both unexpected and predictable consequences. "Predictable" in a sense that we know that something unaccounted for would backfire, "unexpected" because we rarely know in advance what exactly it will be. Larger organizations find ways to mitigate the damage and create new fences... which eventually turn into Chesterton's fences as people forget or discount the reasoning behind them, and into Schelling fences where something becomes a shared norm. And then the cycle begins anew.
I don't have an account there. (Unless you perhaps automatically get one when you register at LW?) I am not familiar with that community and their norms. Making a first post criticizing the community doesn't seem like a good idea.
Also, the problem is a bit more general, I think.
I am reading debates on the Effective Altruism forum, and they seem to focus on how a low-status person might be afraid to refuse to consent to sex with a high-status person, because the high-status person might then refuse to provide them a grant or a job position.
True, but this seems to be just the tip of the iceberg.
Making a high-status polyamorous person angry potentially means not just creating one enemy, but rather a group of enemies -- namely the person's entire polycule. They are naturally likely to trust that person. Even if they have doubts, they still have a selfish incentive not to disrupt their own polycule. And if they often meet and talk in private, the person will be able to tell all of them their version first.
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Imagine the usual monogamous workplace. Imagine rejecting the advances of your manager, and then experiencing retaliation. Imagine contacting HR to complain, and finding out that the HR person handling your complaint is the manager's wife. Would you expect a fair treatment?
Now imagine a workplace with lots of polyamorous dating. The difference is that if your manager is polyamorous, the chance of meeting a member of their polycule is higher, and you probably wouldn't even know. Or you might give up and try your luck at a different company in this tightly connected small industry... but the new manager, or the job interviewer might be a part of the same polycule, too. Perhaps you have just locked yourself out of the entire industry.
On the other hand, joining a polycule of high-status people might be the ultimate office politics move. (Unless you had a bad luck, and the polycule turns out to be two-tiered: the high-status members who treat each other seriously, and the "underlings with benefits" that keep coming and going.)
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This is not about "polyphobia".
I am not saying that monogamy is good and polyamory is bad. The failures of monogamy are numerous and well known, and we have lots of rules created around them. The rules against nepotism were created in the context of monogamy. The rules against sexual harassment were created in the context of (at least officially) monogamy. The archetype of a vindictive rejected man (or a woman) taking a revenge also exists mostly in the context of monogamy. We already know that monogamy can be bad, and we have a set of rules trying to minimize the harm (arguably, not sufficiently, but better than nothing).
I am just assuming that if members of the same species start dating polyamorously, we should expect some of that to happen there, too. And that perhaps we should adopt similar rules. I expect that most polyamorous people are nice and friendly, just like most monogamous people. I also expect that each group might have a few sexual predators.
The main difference is that polyamory seems like it could scale up some of the problems. (Larger group size. Possibility to hit on multiple people at the same time without violating a social norm.) The problematic part is "at the workplace"... but polyamory could be a multiplier of the problems.