People have been able to “afford to question this” since antiquity - it’s not some modern affectation. You see plenty of instances of people arguing for or outright mandating vegetarian or vegan diets dating back thousands of years. I am not sure if PETA’s specific reasoning (“you shouldn’t eat a fish because the fish would prefer you not do that”) is represented, but you definitely see scholars and rulers in the ancient world arguing for a variety of reasons that people should not kill or eat animals.