You also take this oath that binds you to protect the constitution, not the government, and this is what threatens Obama and his cronies.
Here's the oath:
I, (NAME), do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the orders of the officers appointed over me, according to regulations and the Uniform Code of Military Justice. So help me God.
The orders part is further defined to be LAWFUL orders as per the UCMJ. Ultimately, the only source of lawful orders is the Constitution. Should an order be in violation of the Constitution, it is unlawful and anyone who obeys such an order is in violation of everything this country is supposed to stand for.
Obama knows that the military's allegiance is ultimately to the constitution and not his regime, and consequently this is why he has declared veterans and other patriots to be terrorists and has positioned the TSA and his Homeland Security police force as a counter to the military. This isn't about mental health, its about asserting control.