One of the most nefarious facets of belief in progress is that it leads to a moral disengagement from the past. Progress erases the evils of previous iterations of Western civilization through an "ends justify the prior means" logic.
Simple case in point: the genocide of Native Americans was not merely something that happened, it was necessary in order for the US to exist in its present form. Perhaps a simpler case in point: black slavery was not just a regrettable period in US history, it was absolutely essential to produce the present circumstances.
And this is not just a theoretical exercise—it’s intimately personal. Rewind history to the year 1610, remove the slave trade, and then let history play forward again, and not only would the United States fail emerge in anything comparable to its present form, but neither you nor I would exist. Our personal presence on the planet is not independent of the entire history of events prior to our birth.
"But that was then and this is now, and we shouldn’t dwell on things in the past that we cannot change."
But the past has not gone anywhere. It is still with us this very instant, in all of its brutal ugliness, right now, whether or not we have the stomach to acknowledge it. We are all reaping the concrete benefits of eight millennia of genocide and war and slavery and torture and the immiseration of countless millions of humans and beyond countless billions of other beings.
We all were born in sin. But with devout and unwavering faith in progress all of our sins are resolved.