Up to a point, I agree and would like to see the bad and good on both sides, but plenty of people out there have such a skewed view of things that the abolitionists and unionists turn out to be the "bad guys" and the slaveowners and secessionists the "good guys." The logical slight of hand is pretty astounding and if you get exposed to enough of that, and you won't have any problem condemning the slaveowners for their crimes.
Some people assume that "eventually" Southerners would realize that slavery was wrong and "get around" to abolishing it themselves, so that the true crime was the suppression of the rebellion. Leaving aside for the moment the very weighty and disputed question of whether unilateral secession was legal, such a point of view basically gives slaveowners and Southerners a "free ride" based on what one expects they would have done "at some point" and condemns Northerners for what they actually did do. I hope we can agree that that is a skewed way of looking at things.
The abolitionists certainly were often abrasive and sometimes hypocritical, but they do deserve some credit for their insight and courage. Northerners who fought for the union, their country, and the form of constitutional and representative government they grew up with may not have been modern racial egalitarians or 21st century radical libertarians, but they don't deserve the kind of abuse directed against them by those who would whitewash Southern slavery.
We ought to be able to agree that slavery and racism have been American (indeed, global) offenses, that can't be blamed all on one part of the country. But in doing so, we don't have to pretend that slavery was an especially benign institution or that those who supported it were "really" against it in some way, and those who opposed it "really" in favor of some form of slavery or tyranny.
"plenty of people out there have such a skewed view of things that the abolitionists and unionists turn out to be the "bad guys" and the slaveowners and secessionists the "good guys."
That point turns on whether you believe that the South seceeded solely, or even primarily, to preserve slavery.
I don't believe that history will support that interpretation.
I believe that the South had a right to seceed over unfair tariffs and other discriminatory laws, and that they were in the right in resisting Lincoln's invasion to prevent them from seceeding.
"Northerners who fought for the union, their country, and the form of constitutional and representative government they grew up with"
Woah, there. If Lincoln hadn't decided to invade the South to prevent them from seceeding, the United States would still have had "their country, and the form of constitutional and representative government they grew up with." Just with fewer states in it. So don't let's get carried away with the nobility of the north, either.
"by those who would whitewash Southern slavery."
Every time somebody says, "See it for as bad as it was, but no worse," that's "whitewashing" slavery.