My Angel was killed by a cocker spaniel. You cannot tell what kind of dog is going to maul yours just by the breed.
But I agree with you, you cannot live in fear for Badger for the rest of your life. You just have to get past this incident and things will be better. Let your fear decline to healthy caution. Just keep Badger in a pack or carrier until you are sure that where you are is a good place for him to be on the ground.
I am sorry this happened to you, and I applaud your "conversation" with the bull terrier's owners. They need to get control of their beast, and to know that kind of behavior is not right. Sure hope they listened!