War crimes and genocide
The Pentagon agreed with those numbers 2 months ago.
Well first of all, they would have been justified in saying "Death to America" and it would have been constitutionally protected speech. So let's just get that out of the way.
But here is why you didn't have "Death to America" chants. At that time in the mid-1950s, America still had something that was worth saving and holding on to. The blacks at that time were simply fighting for equality and to be able to take advantage of the opportunities that this country offered at that time. There was no incentive to kill the golden goose.
I'm not certain how pervasive these alleged "Death to America" chants are at these protests... I would say, based on your post history, that you are likely exaggerating just how common it is. But to that point, let us assume that those chants are as numerous as you suggest. I would argue that this generation is aware of all of the killing and bloodshed that occurred in America during the civil rights movement and their "mostly peaceful" protests, the killing of millions that we did in Korea, Vietnam, Cambodia, Laos, Yugoslavia, Iraq, Libya, Syria, Ukraine and the livestreamed genocide in Gaza right now. They also have no economic or cultural interest in America because unlike the generation of the 1950s, America is a dying empire that outsourced all of its industrial capacity, is $34 trillion in debt and rising, galloping inflation that makes the traditional American Dream unobtainable and no realist political options in either mainstream party or third party. There is nothing worth saving or preserving. So may as well let it all just crash and burn and start over with a new America. This old one is a rabid dog.