Deer "know" that they are prey; they can sense it and try to run. Since they know it, that means it must be true.
Imagine someone saying "The people I try to steal cars from know that they are potential victims; they can sense it and try to lock their car doors. Since they know it, that means it must be true." Ultimately, if anyone tries to not become the victim of a crime, that means that they "know" they are the victim, so therefore it must be true that they are the victim, which can only be true if the crime exists, and therefore it must be okay.
Obviously, the existence of a type of crime doesn't make perpetrating it morally justified. We recognize the problems with this argument in any other context.