A dog fight typically appears far nastier to the human eye and ear than actually occurs. I would predict that the majority of dog on dog injuries are greater when humans attempt to manage the canine to canine introduction dynamic.
Clearly our domestic companion, the dog, is not wild. At the same time, as confounding as it may seem, he is not human either. The dog is a domestic animal: Present scientific natural history data contends that the longest relationship between the human and the wild started with the Canis species.
With that, there must be a clear division in this one aspect: Humans and canines, although both mammals and social, are not the same at all.
Whereas we humans may meet one another with a forced, pretentious, possible genuine smile and a hand shake; canines introduce themselves with scent, vocalization and body positioning.
In human terms, forcing your potential new found acquaintance to the ground and holding him there would be considered insane at best, but is most likely a crime. At least in a Western society.
In dog terms, the same act establishes nature's "pecking order."
Whereas us humans have a splendid vocabulary and analytics to treat new social interactions "humanly", the dog has only his immediate senses, physical body and experiences to guide him.
The misnomer that female dogs will not "fight" one another perturbs me. I perceive that female on female aggression is as much, if not more, a concern than any other.
However, there is a clear intolerance of male dogs to other males until the "pecking order" is established. Of course a "dog fight" occurs to establish that "pecking order." In my experience, the majority of times this physical expression manifests, it resolves its self in seconds. Once again, I attest that human involvement most definitely will prolong the interaction.
I'm not saying humans should absolutely not interject.
If they are so inclined, I would suggest dog owners study the Leerburg.com video addressing aggressive dogs.
I contend that the information contained within this particular video helped me today.
The more information you have from the most sources you can get, the better you and your dog will be.