Uniform Code of Military Justice, Article 88:

"Any commissioned officer who uses contemptuous words against the President, the Vice President, Congress, the Secretary of Defense, the Secretary of a military department, the Secretary of Transportation, or the Governor or legislature of any State, Territory, Commonwealth, or possession in which he is on duty or present shall be punished as a court-martial may direct."

The standards for members of the military are different than for civilians, and those for officers are different than for enlisted people. Calling Pres. Obama an impostor or a usurper would certainly seem to qualify as "contemptuous words". However, as I implied earlier, the issue of whether or not this person actually exists or is an invention of the writer of this "news article" is as yet unresolved.