I hope the vet doesn't feel bad at all. It's not his fault. He needs to stick by his convictions no matter what, and if other people want to do evil and blame it on him, he needs to have the strength to ignore them. For a vet to kill healthy animals would be a violation of his oath.
Having healthy animals killed is NEVER "doing right" by them. Ever.
It's like the FBI's policy of not negotiating with kidnappers. So a kidnapper says "give me a million dollars or I'll kill the kid", and they stick to their convictions and don't give him the money, and he kills the kid, is it the FBI's fault? No, of course not. The kidnapper made the choice to kill someone, the FBI didn't make him do it. Same for that vet.
From other things I have read, it becomes clear that the guy who did this is a sociopath who enjoys hurting dogs, and is defrauding the Worker's Comp program. I hope he gets what's coming to him.