Unpopular opinion:
You let your baby get attacked because you didn't want to send your dog to an 'aversive' trainer. According to this logic, punishing your dog is worse than your baby getting bit.
There are so, so, SO many things that led to this attack, and SO many things done wrong.
First off: you introduced a second dog to the household, when you couldn't manage your first dog. That in itself is a recipe for disaster.
Second: Instead of teaching your dogs co-existance, you instead completely reorganized your lives to conform to your dogs, through the crate and rotate set up. Now, the dogs are living in an even more constant state of heightened arousal and anxiety, because they can't even see the other animal.
Three: You were nervous about two reactive dogs and a new baby. That was a correct reaction. Instead of punishing your dogs for dangerous behaviours, you decided that 'aversive' training techniques were undesirable, and instead continued to live with reinforcing their daily anxiety.
First: you handled anxietydog incorrectly as well, but since Ranger is the one who attacked, I'll focus on him.
Your biggest mistake: you allowed your dog free access to the baby, even if 'supervised'. NO dog, should be allowed free access to a baby. NONE. Once again, instead of coexistance, you have chosen to reinforce bad behaviour.
Second: You allow your infant to offer your reactive dog food. Instead of discouraging that, or even teaching the dog not to beg, you reinforce the behaviour by literally giving him an amazing treat, and sending him to play in a fun spot.
Third: You encourage Ranger to play in what should be, exclusively the baby's space. The dog should not be allowed any access to your baby's play pen. You need to set boundaries, and this is a HUGE one.
Fourth: Now, Ranger is in his play pen, with a delicious treat, and I guarantee you he was resource guarding. He's growled at the baby before to protect his food, you KNOW he resource guards.
Fifth: Instead of taking Ranger from the Kong, you take the Kong from Ranger, who is actively guarding it. Instead of removing the Kong completely, you instead throw it away, and don't prevent Ranger from bringing it back into the playpen.
Sixth: Now that you've shown Ranger that his Kong gets thrown away when someone touches it, he is even more on guard. He is also on a couch, putting him higher than you AND the baby, giving him a sense of dominance. Baby rushes towards the dog, and Ranger already knows that baby might mess with his food. You already messed with his food. All of his warning signs have been ignored, and Ranger has been pushed past his breaking point and so he snaps, and bites your baby.
Obviously I wasn't there. Obviously I didn't witness this attack. From what the mom has posted though, I can see exactly how this situation could have happened. I'm not posting this to be an attack on mom, or accuse her of doing more wrong than she thought.
The family is traumatized and will probably never be the same after this. I understand that the family didn't know what they were doing, did what they thought was best, but ultimately, they were naive, and a horrible incident occurred.
I am a balanced dog trainer. I use those 'aversive' methods. Properly conditioned, these are not abusive tools, but simply a way of communicating with your dog and offering punishments for undesirable or dangerous behaviours. I have trained hundreds of dogs- dogs who were going to be put down, and by reinforcing the proper behaviours, introducing structure and boundaries, and punishing the dog for undesirable behaviours, those dogs were transformed.
It's not for everyone, I don't expect to change anyone's minds, and I expect some heat from this, but the dog doesn't need to be put down. The family completely mishandled the situation and the dog, and didn't have the means to handle him. They should have rehomed him ages ago. They never should have got him in the first place.
Hopefully some of you read this though, and can at least follow the chain of events. Maybe it'll stick in someone's mind and they handle their dog differently. It's just upsetting to read a story like this, when the situation was completely avoidable.