Ok, so the thought experiment is this:
Taking it as given that
- Muscular neutrality between good and evil is a metaphysically valid position,
- "Good" is "altruism, respect for life, and a concern for the dignity of sentient beings",
- and "Evil" is "harming, oppressing, and killing others",
what justifies a position of muscular neutrality?
In D&D, the cosmos is determined by the beliefs of those within it, so all positions justify themselves (if enough people adopt them). In a cosmos that operated on the ideology of "muscular neutrality," there'd be an existential crisis if there was too much good or too much evil, so the true believer of Muscular Neutrality would be responsible primarily for the continued existence of the multiverse, over all other concerns. If killing this baby or torturing this toddler is awful, that awfulness has a point to it - that it helps sustain the multiverse. Being Good or Evil is choosing to actively court the destruction of the multiverse.
And if the multiverse operated that way, it would be true.
And the best thing to do in that multiverse would be to end it in the paradise of Good winning and then everything ending. A Good person in that multiverse would be a sort of seeker of Nirvana - if existence requires suffering, then we must all flee existence, we must all seek abnegation for everyone. The only peace is a righteous oblivion. The Muscular Neutrality people would oppose this in the interests of existence continuing. They place the status quo - continued suffering - as more important than being Good.
Evil people also seek their own apocalypse - an end of everything in suffering and pain. This is a little more typical for the evil person, but it also requires a bit of selflessness and a cosmic outlook that's not always common. A murderous horde of evil isn't just in it for power or money or dominance or glory. They're in it because they kind of want EVERYTHING to end, to swirl into violence and monstrosity, and then be over, forever, leaving nothing. The Muscular Neutrality people would of course also resist this. Status Quo is their goal; they're effectively the only ones who want the multiverse to continue.
This can make some sense through a Druid's eyes. Like, if you revere the natural world, and have a Muscular Neutrality outlook, the only way for the natural world to continue is to balance the apocalyptic tendencies of Good and Evil. And, that suffering is part of how the natural world continues. In a world suffused by Good, rocks and squirrels and trees and lions could not exist - existence necessitates suffering.
And, yeah, that means that someone who adheres to this ideology is sometimes required to be monstrous, to allow awful things to happen, just to keep the multiverse ticking. Sometimes you need to collapse a civilization in a volcanic pyroclasm, causing untold destruction and loss. If you didn't, well, eventually, that'd be the end of all civilizations. Can't make a Waterdeep without drowning a few Imaskars or whatever.
I'm not sure how people in this cosmology would know how to get that balance right, but maybe there'd be magical signs. Like, an actual utopia that exists and functions and is indeed a paradise suddenly fades entirely from existence and only now exists as legends...but you know it actually existed, before it lost balance and faded (happily) into nothingness. You could see the early signs, as people kind of faded away, or celebrations happened as the land itself bleached and turned to memory.
Some answers I came up with (not that they're particularly good ones):
- There is some kind of Problem of Evil or Free Will logic going on, where Evil is necessary as a counterpoint to good. I don't think this really makes sense as justification for neutrals to prop up dark lords and armies of Evil, and it's too philosophical for my tastes... but it's there, with centuries of argumentation to consider.
"This is the best of all possible worlds" is basically this response. Want a world without pain and suffering? Doesn't exist. It's nothingness. If you like existing, you're going to have to deal with the fact that the world is a flawed and awful place and you don't get to exist in any kind of safety or security. That's not what "existence" means in this kind of world.
Evil has a
Dead Man's Switch and the muscular neutrals are acting in the enlightened self interest of reality.
Variant of 2, Evil and Good can both bring about mutually assured destruction--and this is poorly understood by everyone except the muscular neutrals, who have taken it upon themselves to prevent Armageddon.
Also sort of a variant of 2, the creator of the universe is a stifling and ignorant demiurge who wants there to be Evil in the multiverse. The muscular neutrals are carrying out its will for fear of what would happen if they didn't.
Yeah, all variants on the idea of prioritizing "reality" over just...a blissful nonexistence. The Good in such a world would say, "Remove your attachment to this world and the things in it. If existence requires suffering, then nonexistence is the only solution. If the destruction of evil requires the destruction of ourselves, so be it. We are not that important. We do not have to be."
For me, though this is a viable fiction, I don't find it an especially fun one for most D&D. I prefer to play in a world that needs heroes, not in a world that needs "both-sides" centrism that makes space for being A-OK with boiling grandmas alive in front of their families because the world needs it sometimes. Though the idea of a Good character influenced by Buddhist ideals who pursued a blissful nothingness is an interesting concept, that character concept also works OK in a D&D setting where evil
can be exterminated without ending existence. Though there is something a little appealing about Good characters winning in that setting, a sort of "we're the last ones out of the multiverse, so we'll turn out the lights" kind of apocalyptical bliss and caretaking that is kind of appealing, in a weird, counter-intuitive kind of way.
So, here's your campaign. The multiverse works like this. And, for the most part, Good is triumphing. The Muscular Neutrals and their Evil allies are there, but Good keeps winning. The multiverse is on the precipice of destruction. People have almost forgotten what suffering is like...
but...there's a pocket. A pocket of the rankest, most unrepentant, most depraved evil that the multiverse can still imagine, where Neutrals and Evils are making their last stand. And it's your job to take them out. To snuff out the last embers of evil in this world, and to sort of....eulogize it. To be the last people to remember what it was like to feel the sun or walk in the grass or feel the wind, to be the last conscious beings to love, to bring the last bit of hate to heel. No one else will gaze on this sunset again, and that's going to be a good and lovely thing.
"Ah, it had a good run, this existence."
"A shame about the intrinsic bugs in it."
"Well, friends...we've fixed them."
"And now it's over."
"See you tomorrow?"
"No. And that's the way it should be."