Most other SPCAs would have taken the dog ( SPCA unlimited surrender policy says no animal can ever be turned away), and made it suffer even more than it had suffered alone in a yard for five years.
After keeping it on display in one of its horrifying cells to see if anyone would buy it, it would have killed it if it wasn't sold. As for the next "owner" of this dog...it would be whoever paid for it - no screening, no home checks, no interest except in the money.
The SPCA may be doing screening and home checks now as it claims, but we have no evidence of that. Our own research just last Fall showed that the SPCA is still willing to sell a dog to you even if you say it will be a yard dog.
More people have to be made to take responsibility. This dog was spared almost certain future suffering by being euthanized. The SPCA should not have allowed him to suffer alone in that yard for five years, but most SPCAs would have compounded neglecting to help the dog by killing the dog too.