Sandy - let those who oppose eat dirt. They will never understand what you are trying to say about gradings.
People will always argue (in a cynical stylee) that they only exist for money making. They will always ignore the benefits of a system to the individual that never competes.
They will always argue that it dilutes real Muay Thai whilst never recognising that the real (non Thai) Muay Thai trainers who also do gradings, keep them seperate from the fighter training and keep them in context.
They will always talk to you as if you are commiting a sin by making money, and accuse you (in a round - a bout way) of conning the public if you dare to include gradings in your system.
Blah Blah Blah - they will just never get it mate, so stop trying to convince them!