If you really stop to think about it, these "Masters" have earned their position, one way or another. If they have proper credentials, and have been awarded the position as an instructor, then does it really matter what size they may be? If a overly large instructor is telling you to get on the floor and give him 50 push-ups, then what should be stopping you? Just because he is no longer able to do this, has no bearing on what you will gain, by accomplishing this. If push-ups or whatever are used as a means of correcting an error, who's error was it?
I'm sure if a "master" has earned this position, he has already put in, his share of being in same position, and learning from it.
Did you join martial arts to watch what others are capable of? Or did you join to excell and see what you are capable of? How is it going to benefit you, by having your instructor on floor doing the push-ups, or excersises, or seeing what he is still capable of doing physicaly? If he has the knowledge and the know-how to teach you properly and direct you, then it is YOU who must be working on it. If you truly are questioning a master, soley based on his weight, then I would suggest you "empty your cup" before going in, forget about this judgement, and look with an open mind and heart, to what they truly have to offer and whether you are willing to learn from them, in a respectful, open minded, and loyal way.
I can see an issue, if the instructor is so out of shape that he is not able to critique and supervise properly. Or if his weight should pose serious health conditions and interfers with your training on a regular basis.. But just remember, ones weight, does not determine, ones knowledge.! Isn't it the knowledge of our founders and masters, what we are actualy seeking to learn?
Too many people have forgotten about the "true martial way". Many times, the best fighting techniques learned, do not come from our physical training in the Dojo.. It comes from experience and learning how to be a better and stronger person, inside and out. No matter how strong you get on the outside, it is your learning and knowledge on the inside that will carry you through and bring you the greatest rewards.. You can become ill and lose your muscle abilities, but unless you are brain dead, you will always have that knowledge.. Knowledge is our first and best weapon. Not our fighting skills and power.. Take the time to learn from everyone, no matter their size, shape, disability, or whatever.. It can only make you a better martial artist.
On a final note; One of my favorite "teachers" was a man in a wheelchair, who had been in car accident and left paralyzed from waist down, had spastic muscles, and a speech impediment. And he just happen to weigh around 350 pounds.. He taught me some things, that actualy ended up, saving my life, during a hard battle with an illness.. I guess it goes to show everyone, you never know what you got in front of you, till you are willing to be open enough to seek out it's true lessons. And everyone, no matter what their weight, has something to offer..
Victoria
:asian:
but putting that person aside, I have seen many over weight people do amasing things. Priorities are such that one trains for what they find important. If physical looks are not high on the list so be it. They still condition, train for skill and CAN do it. I weight train and my first Kali Instructoir did not he could move unlike many I have seen yet. Again. some people will never look as if they train yet they do as hard or harder than many others that look great, Others still will be unable to look different as genetically they cannot do as much about their lot in life. 
(wish it was me, I get tired sleeping) 
