"Each public officer who takes an oath to support the Constitution swears that he will support it as he understands it and not as it is understood by others."
The term "public officer" refers to an officer in the civilian government, not the military.
Says General Andrew Jackson, as quoted by Lincoln when he was not yet President.
Again, how does the Military know when to defend the constitution if they are not allowed to understand it? (According to YOUR argument.) Seems like a problem with your theory there.