I don't really think this is a case as simple as judge thedeed though. Greys are trained to chase a lure, and as stated above, they are a sighthoud with speed. If they see a small dog or a cat moving, they will give chase.
They are not human aggressive. I have only ever once witnessed a Grey that was human aggressive and he had along hsitory of abuse to go with it.
It is sad that the public think they wear muzzles becuase they are aggressive though, but I am in full favour of them wearing them though.