I know just how you feel, I too volunteer at 2 local shelters & a ferret only shelter.
It does hurt to see the helpless be blamed for the actions of the irresponsible owner.
I look at the bright side, even if only a few got placed into homes, it is better than none.

And most importantly, yes they lived a short life, but for part of that life they new they were loved & well cared for. I am sure they are greatful for the opertunity that was offered to them. They left for the bridge loved & happy & healthy. I really believe they send little rainbow thankyous for all that you did to make their life more enjoyable.