It's easy to say the owners are shit, but if they are willing to adopt another dog, maybe this dog has a particularity they are not prepared to handle.
Sometimes it is better for the dog to go with people that can deal with their needs.
I think people are angry less because of the desire to adopt to fit their personalities and lifestyle and more the whole go back to the same place their dog is at, say hi, and then wander off with Rufus v2.
Probably strikes right in the center of the Homeward Bound in all of us.