There are only so many ways to respond to horror. Watch the comparison of the responses as two different eras are compared side by side.
There is a radical difference between the two populations displayed in the video. The rare 1945 color footage displays German citizens being marched through a local concentration camp, a place of great injustice that they tolerated through apathy, whereas the contemporary clips are of American citizens marching against abortion. The former stood by as their fellow human beings were slaughtered all around them whereas the latter are taking a stand to end the slaughter still happening to this day.
Why, then, do both respond in horror to what they are seeing? Because this is always the appropriate response to seeing the victims. Whether we permit injustice or stand against it, woe to us if we find ourselves above being moved when we see the butchered innocents.