There is no need for PC in the circumstances you have described. You're saying that you're righting a wrong by forcing white people to respect minorities.
Unfortunately, it's not that simple. First off, you're not actually forcing the respect on those people who committed the prejudices; rather, you're forcing people who have little to do with racism, to respect people that they never derided in the first place. Meanwhile, those who are actually racist just are not going to respect minorities, because political-correctness has no way to compel them to do so. Racism per se is not a criminal offence or civil wrong.
Secondly, that mainly conservatives would find PC abhorrent is also a misconception, because it impinges on free speech, which is, as far as the USA is concerned, something celebrated by both ends of the political (and ethical) spectrum. You say that PC doesn't stop anyone from saying anything, but again, that's not what PC is. I'll say again: to be PC is to not say anything that will offend others. What you're describing as a good thing is straightforward politeness and respect.
The consequences of saying something that isn't PC usually involve being labelled a hater of some shape or form. If I were to state (based on statistics that some 40% of people in prison are black) that most low-level criminals are black, I'd be labelled a racist and not a shred of thought would be given by most, of the value of my statement. As such, there is little room for debate, and what was originally the marketplace of ideas merely boils down to pedantic name-calling by grown-up men and women who ought to know better.