Do you see the "thus" there? It is references what came before it. And the whole thing is prefaced with "Here's the thinking". It is explaining a line of reason

Do you see the "thus" there? It is references what came before it. And the whole thing is prefaced with "Here's the thinking". It is explaining a line of reasoning that leads people to be more suspicious of hitchhikers than they are of people in more mundane situations. Anyway, whether hitchhikers are more often victims has no bearing on the question of whether picking up a hitchhiker is more likely to be dangerous than encountering some random person at a convenience store. Most people are quite certain they aren't going to murder a hitchhiker, so they don't worry about that in deciding whether they'll pick one up.