Is there any part of the marketing or branding of the Mk 26 which suggests that it is the same aircraft as the original? As I understand it the idea is to keep the spirit of the original alive. Does anyone claim to be on a par with an original Spitfire pilot just because they fly a mk 26? I don't believe so!
It may take a certain level of skill to fly the original but I bet it was far from being the most difficult aircraft of its era to fly and I bet there are a few aircraft today which are more of a handful to fly safely!
I really don't understand the reasoning behind the letter. It appears to demonstrate nothing exceopt a rather narrow view of others and an inflated view of themselves.