Australian cattle dog aggressive to dogs and bikers

Hi there,
Caribou, I'm sorry to hear that your dog got attacked by Australian Cattle Dogs.
Of course it is traumatic to see your dog being attacked, especially if that results in your dog being scared of dogs and men after that. However, I know some lovely Australian Cattle dogs and I think it's important not to generalize them all.
Donald, if you dog has a behavioral problem than it is important to make sure that no one is unsafe because of it, including your dog himself.

Lunging and barking at other dogs and people when outside is a common problem and with patience and persistence it's possible to fix.
In most cases dogs display aggression due to fear. Donald, do you know much about the history of your dog? How long have you had him for?
How does he behave at home?
What about when people come to visit you?
How old is he/she? Is he/she fixed?
Does your dog live inside or outside.

Thanks