I don't quite understand what you mean by moral implications. Would I be upset if aliens started eating people? Yeah, that would suck. Would it be morally defensible to fight back in the same way a cow might kick? Of course. But I can't consider their view because they are defined as a higher tier of being in this scenario.

You're imagining little green humans with forks when it may just as well be a hyper-developed cloud of space bacteria. In their view, every human gut biome is a slave pit where trillions can be massacred at will.

Using us as incubators and then harvesting the "human" collection of cell resources is a perfectly ethical thing to do. Who cares about the shrieking sound waves and fluid that spills out while humans melt, that might as well be the smell of fresh cut grass. It's just a bunch of clones of one DNA sequence vs the plethora of diverse cells unleashed from the gut. Easy decision.

Keeping us happy and healthy is crucial for the health of the gut biome, no need to cause any undue stress because that would hurt the final product. But of course, through gene manipulation or artificial selection they can make us into a more durable and docile species.

...And at that point modern humans are effectively extinct. I don't have to worry about the ethics of an incubation vat in the same way you don't worry about our bizzarre and unnatural domesticated crops.

the childish, optimistic look here really just highlights the compartmentalization you have to go through for a "coherent" position.

I'm totally lost here. You're saying a comatose human is actually not a human but it is an animal (and therefore gets human rights)? My "higher thought" point is that our measure of life is relative to human features and human ability. A comatose human is very obviously still a human. Hell, even a dead human is still a human until it decays away and is recycled into something else.

Instead of silly screaming corn: What if I bred creatures that couldn't express pain in any measurable way? Just sacks of flesh that you could herd around and harvest when they're big enough. Slice off some reproductive piece and stick it in a tube to grow the next batch. Basically a meat tree on legs.

Is that unethical? Just because it's gross? It's no different than a plant. What if I told you I made them from pig DNA [no harm was done to the pig btw] but I cut out all traces of sensory organs that might convey pain. They can sense just barely enough to stand upright and only have the barest parts of a brain needed to grow more mass.

At what point does the distasteful husbandry become acceptable gardening? When the creatures can't move? When the red blood is sap? Does the flesh have to be green instead of pink? Do the insides need to taste like a mango instead of bacon? Does it need photosynthesis like a spotted salamander or a sea slug?

Your position is incoherent if you can't tell me exactly where the line is crossed AND that line is solid for all vegans. When does that lifeform gain or lose rights?

If you can't do that or admit there's subjectivity in the judgment then why can't that subjectivity hold for cultures that bred dogs for food? Dogs are clearly not humans, but they're too close to my personal experience of pets for comfort. That clearly isn't the case with all humans, so I can't pass judgment on the mere fact that a dog is eaten.