Having watched the cctv
I dont beleive the owner actually encourages the attack. He appears to have difficulty dragging such a powerful dog off the Guide dog, and resorts to hitting his dog to try and stop it attacking the other dog.
True, a lot of it may be up to the dogs upbringing, but that appears to be a prime case for the bull terrier to be destroyed as its obviously and aggessive dog.
The owner isnt totally innocent - he should have had hold of the lead, and had the dog muzzled, but I dont think it is a "sport" attack like some you hear of
I think the punishment was reasonable - had he encouraged the attack, then that would be a different kettle of fish