But animals eat other animals
Predation describes what happens in nature; it does not establish what we ought to do. We take no other behaviour from wild animals as a moral model.
Eating other animals is not some human invention or moral lapse; it is how life on earth works, and humans evolved as omnivores within that same order. Lions, wolves and eagles kill and eat without anyone calling them wrong, so it seems arbitrary to single out humans as the one species forbidden from doing what predators everywhere do. Taking our place in the food chain is simply living as the natural creatures we are, not a crime that needs justifying.
This is the is–ought problem: a fact about the natural world is presented as a moral conclusion without the premise that would connect them. It is frequently called the naturalistic fallacy, though G. E. Moore's term refers to something narrower: an error about defining 'good', rather than about inferring 'ought' from 'is'.
The disanalogy also matters. Obligate carnivores cannot survive otherwise and cannot deliberate about it; humans can do both. Wild animals additionally kill the offspring of rivals and take mates by force, and nobody proposes those as models. What other species do tells us what occurs in nature, not what is permissible for an agent capable of weighing the question.
Moving from a description of how things are to a claim about how they ought to be, without supplying the moral premise that would connect the two. Identified by David Hume.
How it applies here: Moves from what predators do to what humans ought to do, supplying no premise that would license the step from description to obligation.
Treating two things as comparable when the differences that matter to the argument are large.
How it applies here: Treats obligate carnivores, who have no alternative and no capacity for moral deliberation, as morally comparable to humans who have both.