If he is fighting so that I may have freedom of speech...

He's fighting to protect Bush's Halliburton profits.



...why doesn't he have the same freedom for himself?

Because people join the military ONLY to blindly obey Bush and enforce his infallible doctrines. 



My understanding is that some of the charges were brought because he made a statement to the press.

Specifically, he publicly disagreed with Bush. THAT constitutes high treason.