You did your best, you seriously considered taking him, and when you decided it wasn't best for YOUR dogs, who have to come first, you gave her the number of breed rescue and some training advice. No way is it your fault!!
Danny that is dreadful. It is not in any way your fault this dog was destroyed nor was it your responsibility to rehome it.
As for the people who sent you the PM - shame on you two! That's a disgraceful way to behave; very unkind and also undeserved. Ignore them danny and forward their posts on to admin.
Being locked away in a cold kennel with nobody in sight or within sound reach is completely different to being baby gated or kept out of the bedroom etc.
Hope you have not misunderstood about when I said KENNEL. My kennel is attached to the home and has a 16ft by 16ft compound, is fully carpeted, heated and has music if they want it. Toys available, they also have a paddling pool and sandpit. Mine is certainly not cold, dark and gloomy.