Not much you can do about this if the dogs and the b/f live together and your b/f is hot tempered.
The dogs are obviously afraid of the b/f`s behaviour and are looking to you for protection.
So....if you want to solve the problem, you either dump the b/f or move to another place to live with just you and your dogs.
Unless your b/f decides never loses his rag, things are not going to change at all.
If the dogs are ok with him after the shouting stops, then there is not a lot to be concerned about.
Some dogs do just get upset and scared when they sense hostility between their human owners, which is natural, and the same as any child would react.
But if his tempers get physical, then that`s a different matter.
I`d tend to ignore the dogs if possible when arguments break out, as making a fuss of them Could be making them more convinced there IS something to be anxious about.