Trying to understand...

I have to say that it was not an easy task. I had to read the letter almost 10 times in order to understand it, but I think that finally I did.
If I’m not wrong, Spencer chose King Arthur as his main character because he was a very well-known character, he was seeing as a hero, and he was a person who reflects a lot of different values. I also believe that this is called an allegory because in some way he was making fun of the king by using this story. He chose the Knight of the red Crosse, who represents Holiness, Sir Guyon, who represents Temperance and a Lady Knight, who represents Chastitie. He chose this characters in orden to represents something that was happening in real life but in a sutil way.
He obviously wrote the letter because he wanted to clarify that he was not making was of anyone, but he was only trying to tell an innocent story. He did not wanted to be misunderstood, but I believe that his intention was to play a little bit with this story.