In one easy tweet
The lie Leftist Christians tell themselves is the same lie, or what I once called the myth of myths, that the Left is founded upon. That is, Americans in some way say America is sinless, or flawless, or like God, or perfect, or some such.
As I said many times, I've never known an American to say that. My parents were patriots with the best of them, but had no problem decrying segregation when they experienced it back when my dad was stationed at Fort Hood. Likewise, they had no problem condemning our treatment of American Indians, while at the same time loving our country.
The problem is, the Left sees the sins of America and hates America for it because the Left refuses to see its own sins and admit to them. Convinced they are flawless and without significant or meaningful sin today - today of all times - they can't see tolerating the sins of our country and those reprobates who came before.
And because of multiculturalism, they've been taught not to judge any other cultures or nations, in case conservatives want to point out the obvious. Mongols, Aztecs, Mayans, Assyrians, Huns, Celts, Algonquin, the Khmer, the Han, Hindus, Muslims, Arabians, Buddhists - pick anything out of the Western Tradition, and multiculturalism/liberalism says we don't judge. We celebrate. We look only at those cultures to celebrate them or, at worst, approach them with a neutral, non-judgmental assessment.
If those cultures practiced slavery, or fought wars of genocidal extermination, or practice matricide, patricide, infanticide, or human sacrifice or child sacrifice, what of it? It was their culture and they were all just fine with it. Besides, some might even suggest that such things weren't so bad in other cultures. Slavery? Bah. In all other cultures slavery wasn't that bad; sometimes it pretty awesome. Not like the gas chamber plantations of America's slavery death camps.
And that's just what Ms. Gross is saying. She's acting as if the world of the 19th century was one like liberals want ours to look but doesn't. A beautiful place of peace, love, joy, tolerance, John Lennon songs. Only in America, however, are we beatings slaves (we also beat non-slaves as a form of punishment), or own slaves in the firs place (slavery predated America by ten thousand years and continued in other parts of the non-Western world until the late 20th Century). If it is pointed out that slavery existed in other parts of the world, leftists lie and say it was a beautiful kind of slavery, not like ours (see above).
Bonus observation. One of the cherished lessons I learned in my sojourn with the Orthodox was just how much others in the world hate such things that leftists say. There were Orthodox who are old enough to remember when family members in their memory had been taken as slaves by the Ottomans. They chafe when they hear leftists say things like 'slavery wasn't bad in other parts of the world like it was here.' But then, except for those in the world who want to see the West burn, most of my experience is that people are bothered by many of the assumptions of the American Left. Not that the Left necessarily cares about them, any more than it cares about women now that the latest fad is Transgender.