A few months ago, I got into a discussion with a friend about working out and exercising. Neither of us are pros, but I have a considerable amount of knowledge about workout techniques and exercise in general. I used to work with a Professional Fitness Model who knew virtually everything there is to know about working out, getting in shape, nutrition, and so forth.
On top of the endless conversations I've had with her (the fitness model), I received many tips and was shown how to achieve the best results with various exercises. I understand that credibility is extremely important when it comes to giving instructions. As Humans, our egos are responsible for making sure that we are not outdone by an inferior subject. We tear apart and break down anyone who claims something in which they have no apparent credibility.
What I am getting at is that, to my friend, my above-average knowledge of working out and exercising is rendered useless. I am not a licensed trainer, and I don't have the physique to compliment the knowledge. Does that mean that my word (aka advice, suggestions, etc) cannot be trusted? After the days of combined online research, professional guidance, and the months spent at the gym, would one still rather hear it from a licensed professional?
Credibility is believability. In cases such as this, your word may not be as worthy as that of an actual professional, regardless of where or how you acquired your knowledge/experience. Why is something like this so complex? Just because I don't have Arnold's body doesn't mean I know any less than he does. If Socrates personally asked me to spread his words of wisdom to others, would people believe it coming from me?