A cat, unless the dog is much bigger, can really mess up a dog. They can use their front paws like a boxer, they have so much flexibility, it's like they've all been trained in some special gym somewhere to fight. The dog has basically his jaws and not nearly as much variety with their paws. My cat, when you put your palm on his head (easier sadi than done) will bob and weave his head to get out from under it, and will lash out with both front paws. He's thinks he's a badass.
Gerald McClellan is/was indeed a sick man to do those kind of things to dogs. A lot of the great fighters have severe mental problems..."normal" people dont become greats in the ring imo. The true killer instinct of the best fighters is something that is not appreciated anywhere else in society which is why a lot of these fighters fall apart when their fighting days are over.