No, this expansion is not useful. It's like expanding the use of the word "bread" to include bananas. You still need a word for bananas, because while both are starchy, they are nothing alike in other ways, and the distinction is useful. Words DO mean things, and misusing them alters your meaning.
So, people collectively agreed that it's a bad thing to marginalize and persecute individuals based not on their personal qualities or actions but on membership in a persecuted minority. They came up with a term "political correctness" to designate avoiding doing that in everyday speech.
The reason this is a useful term is because it designates a specific category of speech/action which people have collectively decided is NEVER OK. This is different from offending people in general. People can get offended at just about anything you do or say, or even at something you are. That doesn't make their feelings of offense automatically reasonable or put you automatically in the wrong / make you worthy of condemnation.
So inflating the term "political correctness" to mean "never offending people for any reason whatsoever" is not useful or reasonable. You are building a straw man and raging against it. People who rope in political correctness to demand a right to never be offended are doing the exact same thing, just from the opposite side. The point is, nobody has the right to never be offended, not even members of persecuted minorities (for instance, you can feel free to insult a black person so long as you refrain from using racial slurs, because doing so points to you having a problem with them personally rather than their race in general, so you are being politically correct while doing it). That doesn't mean it's acceptable to join in on the persecution of minorities. If you insist on conflating these things, you basically undermine your own ability to argue against stupid and entitled individuals because you've already conceded that they are apparently asking for the exact same thing as persecuted minorities who don't want you to use slurs against them.
Yeah, I missed the word NOT in there. Excuse me, what I meant was "NOT speaking truth to power is the exact OPPOSITE of what political correctness means". But thank you for carefully avoiding my point that speaking truth to power has nothing to do with political correctness or lack thereof. Powerful people are not a persecuted minority, therefore you can offend them to your heart's content without being politically incorrect.
Now, I'm not sure which USA you live in, but the one I'm living in still considers "black" to be an acceptable term to designate people of African descent. There is even a voiciferous opposition AMONG blacks against the term "African-American" as othering, condescending, and an example of "euphemism treadmill".
The examples you give, however, "Negroes have been sorely oppressed throughout much of American History." and "African-Americans are just lazy, and predisposed to rely on welfare and handouts." are BOTH politically incorrect. One because it uses the word "Negro", which is considered a slur because of its historical use, and the other because you are using a harmful and untrue stereotype in order to vilify an entire group of people regardless of their personal merit.