He's not entirely unaffected, but there's no denying he'd been predisposed from the start to compartmentalize and keep his distance from what he sees at work. Reid takes some of it home with him, for sure, but not nearly to the extent that it would be prohibitive to his job. He's well aware it takes a certain kind of person to handle what they see every day at the BAU, and keep coming back for more.

In fact, he opens his mouth to answer, and then pauses, and thinks better of it. The other answers he has are, in some ways, actually worse than serial killers.

"Are you sure you want to hear? We're supposed to eat. Not everyone can eat dinner while looking at crime scene photos. Metaphorically speaking." This level of consideration is purely Garcia speaking. Reid's sort of trained to think of how it affects other people.