Thinking about killing goblins

Well, when you're like ten and your entire village is burned down by a goblin war band and the last thing you see is your older sister getting raped to death by goblins you might get a little messed up in the head. When the person who finds your unconscious body and decides to rescue/teach you is a hobbit with a murder-bonner for goblins strong enough that most of his clothing is goblin-skin leather you might get more messed up in the head.

In essence Goblin Slayer's past messed him up enough that the narration of the original light novels constantly refers to him as a boy in spite of the fact that he is an adult, and has been an adult for half a decade as far as his setting/time period is concerned. (He's about twenty, in a setting/time period where you are considered an adult when you're around fourteen/sixteen).

So he may not be autistic in the sense that he was born with a mind that thinks differently, but the experiences he was subjected to in his formative years did bend his thought processes in a manner an observer might call autistic.