Defensiveness, in horses and in people, is a sign of insecurity. If you are truly secure in what you are doing, then there is no need to defend it since the proof would be in the work.
I liked what Jhinnua had to say. A big determining factor in who you chose to listen to is determined by what you are looking for in your horse and your relationship with them. I was talking to someone the other day who told me that in making progress, every student must kill their mentor (metaphorically of course). It means that you must outgrow them in your progress and develop your own way of thinking. She was saying this as looking at my past experience with horses. Now, I'm not saying that I know more than any of my previous mentors, and I am still on good terms and talk regularly with all of them and I still have a great deal of respect and gratitude towads all of them, however there came a time in the training process where I was no longer in need of them and went searching for new blood. It is my goal that my students will do this and they will be so secure in what they are doing that they will begin to question what I am doing and develop on their own. The changes that you recognize and make for yourself are the changes that you will remember the most.
I always laugh when people see my horses and ask what "method" I follow, and I have actually grown quite disgusted with the word. The more I'm around horse, the more I realize that they do not follow a rule book. I too often see people get lost in the method and not see the horse, or a horse get lost in a method and not be able to see beyond the method. When I walk into my barn or pasture and heads turn wanting to be pulled out first I start to think "what method do I use when I go to lunch with a friend? or when I help friends that own a local restaurant?" There is no method, I communicate, do my job, and help others do theirs. That is the same thing that I do with horses, there is no method behind getting them to go in a circle or jump a barrel, just years of learning the language first hand.
Horses are not video games that you push this button and this happens, or "if you have this version, then you must do x and y to get z result". I personally would feel quite insulted if someone were to talk to me that way. Don't get lost in the method, get lost in the horse. If you take the time to listen, they will let you know exactly what needs to be done.
I'm not saying to go it alone, watch every show you can, read every book you can, audit every clinic or lesson that you can, but never lose yourself and always be prepared to "kill your mentor".