My comment on the Dane not being fixed was meant to be more of a reflection on the owners lack of responsibility for the dog and the breed in general. What I didn't mention is these people's intent to breed her, because they want another puppy. They are back yard breeders in the making!
As soon as the trainer heard this she was totally shocked. She began to explain to them the that to be responsible to the breed, they need to get their dog hip certified etc. before even considering to breed. They also had no clue that keeping a female intact without breeding increases many health risks.
I am by no means saying that keeping a female intact is "the root of all aggressive behaviour". I don't have the experience or knowledge to make any such statement. I did say that this dog's actions were much more out of control than aggressive.
Just a question, since I don't have the experience myself, wouldn't a dog coming into heat react differently to two other bitches, one of which, the GSD with whom the lunging and barking was happening with, is old enough to be in heat herself?