I feel it's fairly straightforward - we've been eating animals since caveman times, and it's (or was) a necessity of life. Many cultures have various rituals around killing the animal, making sure it's painless (that's what halal was for it's time), thanking god for the bounty or whatever. Obvious modern context is different, but still.

Oil is 'food' for machines, and it certainly doesn't need to come from live creatures. To steam alive penguins by the thousands to produce measly 400g of oil, while wasting the rest of the carcass - that's barbaric. This whole process has simultaneously Nazi and Matrix vibes to it.