I know you said no one bullies your piggies, but clearly 2 dogs just did.
As the owner of many dogs over the years I can safley say that shoulting loudly at your dog will not stop it barking at your piggies again.
I had a dog that required 52 stitches after being attacked by a cat, and it did not even make a dent in his desire to chase cats.
It is important that your piggies can feel safe in their own home, and you need to make sure there is no way that the dogs can get into the same room as them.
Imagine if such a thing happened when you were not at home?
I know of several members who use baby gates on their piggy rooms, solely to keep their dogs separate at all times from their pig.
You might want to consider this as a possible option for the future.