Some of this is management of people's expectations when they become involved with the game, and what the overarching expectations of the community vs the administrators are when putting together events or quests. I'm always interested in having more people to RP with, so it does make me a bit sad that people have or are thinking about leaving Glom for this reason. But let's sort of forget the Glom lore for a second and go a bit meta.
In a fantasy-type game with PvP, PvE, various classes that heavily involve manipulation of death/dying (necromancy, most sterotypically), it is an expectation that one can expect to see and/or participate in violent acts against humanoids. Completely expected from basically 100% of people who are in the game or even have just read about the game. We as players (and I think I speak for everyone here) don't condone murder in real life, obviously, but this is an expectation in game.
What's not expected when reading about/participating in the game is a requirement to participate sex, sexual assault, rape, etc. even though there are examples of sexual assault in the lore (most prominently, how Glom's own native race, the faelings, were created). We're not a sex-themed game! We're a PvP-RP fantasy-steampunk game! Accordingly, it would be absolutely beyond the pale for admin to expect players to participate an sexual act as a requirement in game and the community at large would not accept it. So bringing up that I feel is a strawman.
The core question is, despite the prominence and expectation of other extreme acts of violence within the game, is the active murder of children acceptable in the context of the game?
The admin, with the inclusion of the baby-killing, have said, yes, this should be expected. And taking it a step further, they feel it's so integral to the game world that literally the most powerful free artifact obtainable in-game for a member of Glomdoring is gated behind this one requirement.
And if everyone in the community felt that baby-killing was a bridge too far (like say, if summoning Night required on-screen graphically, anatomically detailed rape), we wouldn't be having this discussion, would demand point blank there be a change to the quest, and the admin would acquiesce.
I think Moi's example is illustrative on how the Unity Plague, while within the expectations of what Lusternia is, can be difficult for players to deal with. There will always need to be a balance of how many people the admin can afford to alienate to advance their vision of the orgs and their world at large because there will always be people who find certain aspects of the game unquestionably intolerable on an OOC level.
For me, I will also mention that there will always be a need to balance the lore world with the game mechanics. My take on this, not like it matters, is that extreme violence is an integral part of Glom (and Mag!) lore and should be preserved and disseminated. However, I'm not sure baby killing is so integral to the game world such that literally the most powerful free artifact obtainable in-game for a member of Glomdoring should be gated behind this one requirement. And I know I'm not addressing the point that Versalean and others are trying to make with bringing this up, but since I'm not particularly triggered by stabbing a baby with my e-knife, I don't feel like I can use their line of reasoning to justify my thoughts on it. One way or another, I'm basically meh. Baby killing for the orgbix isn't going to be the hill I die on to defend the integrity of Glom lore. Perhaps I have an overly rosy view of what others think represents Glom lore, but I think what we bring to the game is much richer than just, 'hey these dudes are willing to kill a baby damn that's cool'.
edit based on Xenthos's post below regarding accuracy of naming the quest in question and to emphasize my relative indifference