It really comes down to Hope.
If you believe the world has completely ended and it's time for a new dark ages then kill them.
If you believe that we can rebuild the world from this disaster and that one day things will get back to normal with barbecues and birthday parties then you should spare him
I am Sir Jay of RedBull Head Scribe and Knight
charged with Protecting the Queen,Penning tales for the Queen ,
Keeping Milo from going further insane,Keeping an Eye on the K.O.P.
Mentored by Tom Lehrer's Ghost