I wouldn't be scruffing any dog showing aggression unless it was the size of a cat or it was brachy like the Pug. I don't believe in alpha rolling either (assuming this is what is meant by 'tking a dog to the ground' ).
Dogs are dogs. They're not machines. They have insitincts and natural behaviours that even the experts can't always understand. How a pet owner is meant to understand them I'll never know. Dogs are never bombproof or predictable either on or off lead.
The fact is we have dogs, we have off lead areas and we have people who don't put leads on them when they should (ie. as is required by law). We can all only be prepared as much as possible and attmept to control any dog as best we can.
Would I jump in front of a dog coming at my Pugs? You bet I would and I would be pumping with adrenalin hoping I could ward off, stop or prevent an injury to me or my dog.
Would it worry me if a dog rushed at my dogs? Of course it would, and I would take evasive action in the hope it prevented an attack.
Whose responsiblity is it? If my dogs are on lead and under my control, then I would think responsibility lies with the attacking dog's owner. I would expect that they would assist and come to my aid in separating the dogs or stoppping the attack. If the owner had experienced problems like this before then I would nail the bastards for being so irresponsible. If it was a once off and unexpected I would hope they learnt somethig from it and looked for ways to prevent such a thing recurring.