Re: Protective Aggression?
I would call in a trainer. I don't think this is behaviour that can be tolerated at any level. We have seen Stevie Ray exhibit aggression to an older Shih Tzu we have. She is 14, rescued and a resource guarder. We deal with both dogs behaviour. However, because Steve is big and can do serious damage we do not allow her to behave this way. She is always redirected when she starts picking on Zoe. Zoe is kept out of the area when we are eating as she would go after Steve and one other dog we have. We have also put Zoe on Clomicalm.
You may also want to reconsider him being in daycare, or at least this daycare. They do not seem to have a good handle on dog behaviour. The other thing that screams out to me is that although bullies are protective it is not their job to protect us, rather it is up to us to protect them. We call Stevie off all the time, telling her it is not her job.
Has your boy been socialized with other dogs besides the daycare? Does he live with other dogs?