I have been in "management" for many years from shop floor through to operations.
I dont like that letter at all, you would be far better going to see your HR representative in person or if need be phone them. That letter is open to so many negative interpretations for the reader, racist, whinger, trouble causer, problems with authority. I am not suggesting you are any of these but it will be interpreted in different ways depending on the reader and their mood at that time. In person works better every time and only stick to fact not feelings.
Just my thoughts.
Good luck on what ever you decide