Rainforest is not a good analogy, imo. It presumably is an important part of an ecosystem and also sort of a nature’s museum. Farm animals are absolutely synthetic and barely play any positive role in ecology. So if you cut a single farm animal, I don’t see why 8 billion others shouldn’t do that or should feel bad doing it.

All that said believing no animals should get slaughtered. If we do it to some, could as well do to many. See https://news.ycombinator.com/item?id=42642138 tld: I don’t believe in reducing numbers, because the reduced numbers mean nothing to the animal being slaughtered.