I dont think there is a right or wrong, you cant look down on someone because they love their dog.........thats just plain madness, but at the same time you cant dig a bloke out who wont except second best either, if its not working for him then its not.
The person who will move on has to feed the thing, pay the diesel, clean up the shit so he has every right to make that call IMHO............Its OK rehoming these things, and I have done it twice but only because I was sure and the dog had done nothing wrong,
But if a dog is genuinely not up to scratch, why prolong the agony............a