Is gelatin a by-product or are animals specifically killed or harmed to obtain it?
Thinking about animal products in terms of whether the animals are specifically killed for them is the wrong way to approach it I think. Byproduct is not the right word for items like gelatine and rennet; while animals are not killed solely to produce these items, they are are far from being an incidental part of animal agriculture. These secondary items help make the exploitation and slaughter of animals a profitable concern, it just isn’t the case that these items have no impact. Animals aren’t specifically slaughtered for any one product, we take everything from animals, meat, milk, skin, fur, sinew, fat, muscle, organs- everything. That some products are secondary to what is being produced does not make them any less unethical.