In Looper, it is established that permanent physical harm to a young looper will instantaneously affect the old version of the same looper. For example, a looper can send a message to his older self by permanently carving it in his arm.
I assume Abe and his gang know about this. Why is it, then, that in Seth's case:
when the killers capture young Seth, they torture and mutilate him in order to force old Seth to come to them, then end shooting him up? Wouldn't simply killing young Seth get rid of both Seths? Is the torture simply sadism?
We know the above will happen, since something similar happens later in the movie. And if Joe, who is definitely not the sharpest tool in the shed, can figure it out, surely Abe must also know it?