"Everyone does it" translates to "I don't think I will suffer consequences from doing it". It's a justification based on self-interest, not ethics. It looks li

"Everyone does it" translates to "I don't think I will suffer consequences from doing it". It's a justification based on self-interest, not ethics. It looks like they are applying a version of Kant's Categorical Imperative, which is roughly "what if everyone did it?" The justifier is saying everyone does do it and everything is fine. The proof is in the pudding. But as you say, if literally everyone did it, they wouldn't be having this conversation with you. So what they mean by "everyone" is "enough people that I'm safe".