That must have been satisfying to write! My advice would be either to try to hit a humorous "I'm not taking myself too seriously" tone in the letter for fear of seeming to rise, or to keep it very very short and contained: "Dear Sir, would Jim Bloggs have complained about someone Walking the Wight in traditional costume of any other culture? Yours, etc." On the other hand, your local rag might have a tradition of printing rants...