Good question. It shows some pretty neat thinking. (By the way, did you get this question from a textbook on logic and then adapt it for your purposes here?) Your question is interesting in that it involves logic, philosophy, linguistics, pragmatics, and English language usage in general. I think, however, you might be confounding your question with too many variables, each one of which requires additional "unpacking."
In order to compare apples with apples and oranges with oranges, we need to separate some key variables. You've laid out the variables for an Oreo's staleness quite well. On the traditional X/Y axes, on the X axis you've got soft/mushy and hard/dry at opposite ends. (Let's presume there are degrees of softness/mushiness and hardness/dryness as you travel along the axis.)
On the Y axis you've got humidity, low to high. Plot a graph and you've got a 45-degree angle sloping from the top left to the bottom right. With high humidity comes high softness/mushiness; with low humidity comes hardness/dryness. Simple. You could, however, complicate things by adding more variables.
This, then, may be at the heart of your "dilemma." I say: take things apart; work with just two variables at a time; play with them; attach antonyms to a given phenomenon one pair at a time. You'll find out pretty quickly that in working with feelings and attitudes, things get complicated very quickly!
Take your "political correctness-to-an-extreme" example. You have the opposites of political correctness and incorrectness, but can you graph them one at a time the way you would the staleness of an Oreo? Frankly, I can't think of what the Y axis would be if you were to do so.
Perhaps we should stick to two simple horizontal continua: 1) "political incorrectness," and 2) "political correctness." Let's take them one at a time.
Political incorrectness could be labeled "reactionary" on one side of the continuum and "radical" on the other side. In other words, at one extreme you have the person who believes in no form of political correctness, and at the other extreme is the person who goes overboard, or over-compensates. So far, your Oreo analogy is holding up pretty well, since there are varying degrees of political incorrectness, just as there are varying degrees of staleness for cookies.
Now do the same for political correctness. What do you come up with? It's tricky, is it not? Until someone comes up with the definitive list of criteria by which political correctness can be measured, we're left only to guess what the "ideal" and the "not so ideal" are. In other words, what comprises Aristotle's "golden mean"? Moreover, who is going to come up with a measurement, an objective standard, by which the phenomenon can be measured and evaluated?
I guess our country's founding documents, particularly the Declaration of Independence and the U.S. Constitution--particularly the Bill of Rights--might be a good place to start. Interpretations of these seminal documents do vary, of course, which is why we have Republicans and Democrats!
To wrap up, words are funny things, especially graded antonyms (stale/fresh, PC/non-PC, beautiful/ugly, unique/common, selfish/selfless, proud/humble,etc.). On the one hand, it's relatively easy to understand the staleness of an Oreo cookie by labeling it soft/mushy and hard/dry, but try doing that with something as complicated as political correctness. You might think at first blush it would be easy, but contraire mon frère!
Who is to be the final arbiter of what constitutes political correctness? What are the standards by which one measures its opposite? Are they truly opposites, or can political correctness be another term for "It's OK to do anything you want, as long as you don't hurt someone"? I wouldn't call that political correctness; I'd call that stupidity--or perhaps to use one of your terms, "apathy."
We all draw a line in the sand on various things and say, "Here is where I stand; I'll go no further, at least until someone can persuade me otherwise." (Some folks do not add the part about persuasion, because their minds are made up, period!) Even the person who refuses to draw a line in the sand has already done so by default, and that line to him is, ironically, "no line" at all. Hey, if you don't take a stand for something, you might just fall for anything!
Probably the only thing I have done in this "answer" is complicate and confuse things unnecessarily--muddy the waters, so to speak. Perhaps I have laid a foundation someone else can build upon. At this point, I'm a little ambivalent about what my feeling state is about my answer, but you and others are welcome to join in the fray.
By the way, you might want to check out Brad Syzone's unanswered question about half-graded antonyms.