Which means that many doctrinal authorities are capable of making stuff up.
Friend, I'm assuming you believe all/most of religion is made up anyway, right? I mean, you might think some of it was made up sincerely and some was made up cynically. But you know with an extraordinarily high degree of certainty it's all made up. Right? So who cares who made it up. It's there. Some people take it seriously.
It doesn't threaten non-theism at all to concede that religions define their own interpretations and belief systems. This concession is actually the bread and butter of non-theism. Really the only person who gets to contest that is the theist with an alternate interpretation, because he can appeal to a higher authority.
Even though I said I didn't want to sling scripture, and I really don't: why don't you muzzle the ox that treadeth out the grain? Why were the fifth and sixth days of creation declared good? Why was man created on the same day as the beasts of the field? Why was man originally given plants to eat, not flesh? Why was man specifically forbidden to eat "the life" of the animal? Why did you have to rest beasts of burden on the Sabbath? Why couldn't you disturb mother birds on their eggs? Why did fallen beasts of burden have to be helped up? Why were the animals saved with Noah during the flood? Why doesn't God forget sparrows? Why does God feed the birds of the air? Why is it that animals only become carnivorous after the exit from Eden? What does it mean that the lion will lie down with the lamb and that a little child shall lead them? Why are humans constantly portrayed as animals in scriptural metaphor?
Now, I totally believe you have answers for all these questions that acknowledge the scriptural references but manage to discredit their supposed connection to any sort of authorial concern for animal welfare or the environment. The problem is, that's not enough. You have to show that your answers were the one that audiences have understood and adopted over centuries. That will be difficult. It certainly appears that St. Francis and St. Augustine and St. Aquinas and Cardinal Manning and Tolkien and John Paul II disagree with you, and I'm inclined to say that their readings carry more popular weight than yours.
But you're not following the implications of this.
Oh, no, I get it. Respect for nature != concern for the pain of creatures with nervous systems. Spiritual environmentalism is nothing like utilitarian environmentalism. I just don't care about that very much. I am much more interested in whether some secular environmentalists will eventually develop secular justifications for assigning "rights" or something very like that to aspects of the environment that lack nervous systems. Probably not worth chasing that rabbit, tho.
Even though I said I didn't want to sling scripture, and I really don't: why...
That's a cheat that is commonly used by creationists who come up with lists of 100 and 200 arguments for creationism. The trick? Make a list containing a lot of very low quality arguments in the knowledge that it's long enough that no one person will have the patience (or sometimes the knowledge) to properly refute every single one. Then latch on to whichever ones got the least thorough response.
It's not hard to point out the flaws in your examples. For instance, Noah did...
When someone complains that utilitarianism1 leads to the dust speck paradox or the trolley-car problem, I tell them that's a feature, not a bug. I'm not ready to say that respecting the utility monster is also a feature of utilitarianism, but it is what most people everywhere have always done. A model that doesn't allow for utility monsters can't model human behavior, and certainly shouldn't provoke indignant responses from philosophers who keep right on respecting their own utility monsters.
The utility monster is a creature that is somehow more capable of experiencing pleasure (or positive utility) than all others combined. Most people consider sacrificing everyone else's small utilities for the benefits of this monster to be repugnant.
Let's suppose the utility monster is a utility monster because it has a more highly-developed brain capable of making finer discriminations, higher-level abstractions, and more associations than all the lesser minds around it. Does that make it less repugnant? (If so, I lose you here. I invite you to post a comment explaining why utility-monster-by-smartness is an exception.) Suppose we have one utility monster and one million others. Everything we do, we do for the one utility monster. Repugnant?
Multiply by nine billion. We now have nine billion utility monsters and 9x1015 others. Still repugnant?
Yet these same enlightened, democratic societies whose philosophers decry the utility monster give approximately zero weight to the well-being of non-humans. We might try not to drive a species extinct, but when contemplating a new hydroelectric dam, nobody adds up the disutility to all the squirrels in the valley to be flooded.
If you believe the utility monster is a problem with utilitarianism, how do you take into account the well-being of squirrels? How about ants? Worms? Bacteria? You've gone to 1015 others just with ants.2 Maybe 1020 with nematodes.
"But humans are different!" our anti-utilitarian complains. "They're so much more intelligent and emotionally complex than nematodes that it would be repugnant to wipe out all humans to save any number of nematodes."
Well, that's what a real utility monster looks like.
The same people who believe this then turn around and say there's a problem with utilitarianism because (when unpacked into a plausible real-life example) it might kill all the nematodes to save one human. Given their beliefs, they should complain about the opposite "problem": For a sufficient number of nematodes, an instantiation of utilitarianism might say not to kill all the nematodes to save one human.
1. I use the term in a very general way, meaning any action selection system that uses a utility function—which in practice means any rational, deterministic action selection system in which action preferences are well-ordered.
2. This recent attempt to estimate the number of different living beings of different kinds gives some numbers. The web has many pages claiming there are 1015 ants, but I haven't found a citation of any original source.