I have been researching this since last night, and in every instance it is accepted that this language is referring specifically to military installations.
You are not defending the words of the Constitution. You are defending those who have twisted and manipulated the meaning of those words.
It's trivially easy for a noble Horatius or two to divert attention from the grievously Despotic actions of the tyrannical Police State and over to the treaty of Guadalupe Hidalgo.
No, we have a situation where swarms of officers are harassing Cliven Bundy and other citizens, and eating out all of our substance paying million-dollar contracts to government mercenaries, ala the Hessians, and where the King's Men are setting up "First Amendment areas", and beating up and arresting people for "resisting arrest".
See my post #331 on the thread Nevada rancher's son freed, BLM collecting cattle for an in-depth analysis of the actions of these "Constitutional" Horatios-at-the-Bridge:
http://www.freerepublic.com/focus/news/3142500/posts?page=331#331
These Horatios are all over the Cliven Bundy threads arguing for "Federal property".
The first portion of this pertains to the establishment of the District of Columbia (not to exceed 10 Miles square). The second portion gives the U.S. Government the authority over all places established with consent of the legislating body within said state. So your repetition of this particular clause in the Constitution is a moot point, as it is referring to all places and does not apply in this scenario.