they're in the dictionary, sure, but not with the meaning that FReepers often attribute to them. At least not in any dictionary thet I've seen. What definitions does your Websters give?
http://dictionary.reference.com/search?q=subject shows subject to be
"One who is under the rule of another or others, especially one who owes allegiance to a government or ruler. "
and citizen to be
"A person owing loyalty to and entitled by birth or naturalization to the protection of a state or nation. "
whereas Freepers usually base their definitions around whether or not a person can own a gun for self defence or not. Before WWI Britons had liberal gun laws but definitely were subjects. These days we have harsh gun laws but are citizens. The 2 just aren't related, unless you wish to redefine the words, which is what has happened on FR. nothing wrong with it of course, but is still a slang meaning.
In my original post, to which you respond, I specified the dictionary W7NCD.
"subject: one that is placed under authority or control" Disarmed, you subjects have no means with which to resist the tyranny of the state.
"citizen: an inhabitant of a city or town; [i]esp[/i] one entitled to the rights and privileges of a freeman."
In each case the definition is the first, hence preferred, of the listed alternatives.
The state collects taxes at the point of a gun with our, your's and mine, permissions. I may die a freeman in a disagreeable confrontation with the state. You have no arms (goes beyond mere guns) with which to resist your state. Indeed, it'll likely be a recent immigrant at your doorstep begging, as agent of the state, to be killed.
See my tag line.