Cynthia - the op wrote "However, when Mac gets to close to Sadie any other time, she attacks with a full on chomp." THIS IS NOT FEAR BASED BEHAVIOR - it is pure dog on dog aggression due to territory guarding (most territory or resources guarding is NOT FEAR BASED) it is pure aggression and MUST be dealt with ASAP. To correlate putting a dog into a submissive position in front of the dog it has attacked is mimicking a natural behavior among dogs. It is not beating a dog, it is not rough handling or aggressive on my part - it is simply rolling a dog onto its back and holding it firmly yet gently until it calms down. I resent your implications. And as far as your comment about MOST reactions "we see in dogs" being fear based negates a HUGE number of dogs who have behavioral problems. It is naive and dangerous to make such assumptions. Many dog owners need to be firmer with their dogs however if a dog reacts negatively to a firmer voice,or firmer mannerisms then training must be adjusted in order to work effectively with that dog. I can find a hundred web sites or training manuals to validate my suggestions to this OP.
As with EVERY poster here and the people I work with on a regular basis, I am very careful about what I recommend to each dog owner - I am a firm believer that each dog needs to be assessed differently. YOur blanket statement about fear based aggression is ignorant at best.