The only thing people will say that annoys me is the "but animals eat other animals" argument from otherwise intelligent people (no worries if children say it). I've yet to meet someone who sincerely thinks that what happens in nature is ethically okay (as a simple point, many animals will eat their own family when stressed and sexually assault each other constantly, which are very natural but obviously unethical for humans to do. I've seen animals torture and eat each other alive) so the whole argument is a waste of time. It's weird that the "it's natural" argument is probably the most common when many people will walk it back even before I point out the flaws.