I'd say that (admitting treason) would be a definite drawback to the defense.

But, that being said, and all kidding aside, the guy knows he won't "get off" and probably will get a death sentence anyway. So, why not go down in a blaze of Islamist glory - as a warrior for global jihad ?

In essence, that is what KSM and his compatriots expressly stated in 2009 (my 2009 post, KSM's Islamic Response; and their manifesto, “The Islamic Response to the Government’s Nine Accusations”); they sum their argument as follows:

With regards to these nine accusations that you are putting us on trial for; to us, they are not accusations. To us they are badges of honor, which we carry with pride. Many thanks to God, for his kind gesture, and choosing us to perform the act of Jihad for his cause and to defend Islam and Muslims. Therefore, killing you and fighting you, destroying you and terrorizing you, responding back to your attacks, are all considered to be great legitimate duty in our religion. These actions are our offerings to God. In addition, it is the imposed reality on Muslims in Palestine, Lebanon, Afghanistan, Iraq, in the land of the two holy sites [Mecca and Medina, Saudi Arabia], and in the rest of the world, where Muslims are suffering from your brutality, terrorism, killing of the innocent, and occupying their lands and their holy sites. Nevertheless, it would have been the greatest religious duty to fight you over your infidelity. However, today, we fight you over defending Muslims, their land, their holy sites,and their religion as a whole.
The specifics of their argument prove that they consider themselves to be lawful combatants under the only law that counts to them - the Koran. Hague-Geneva are not material to them because those are man-made laws. National citizenship is also immaterial to them because only religious citizenship counts. Zawahiri, UBL and Maj. Hasan's mentor al-Awlaki all made these points very clearly.

So, it is scarcely surprising that Maj. Hasan is trying to follow their playbook.

Regards

Mike