Guilt isn't necessary to be annoyed at someone's word choice. The chosen words are presenting an implication that eating animals is morally wrong, and if someone doesn't believe that and eats animals then they are right to be annoyed by the implication that they are acting immorally. No guilt necessary.

Or make them snappier two-liners, like you?

> they are right to be annoyed

Annoyed is an emotion. Someone's words triggered that emotion. Annoyance typically comes from someone's boundaries being crossed. One person might say, "Eh, murder/kill, whatever," but for some reason it triggered a deeper response in you. What do you think is behind that? You probably won't reply, but if you're a fan of metacognition, try tracing that emotion back by asking yourself why? every time you think you're done. Annoyance isn't a primary emotion, it is a response to one ore more. You have to be conditioned to be annoyed by words, unlike, say, mosquito bites. What makes you annoyed by it?