Earlier quoted context omitted.
Can you see how a reasonable person might read this as catastrophizing? The tweet you linked to is pretty banal, and appears factual. I'm having trouble even connecting the dots from "many of the founders were slaveowners" to "let's cancel America". The nuns taught me the same thing in 1980s Catholic grammar school.
It would be a perfectly fine observation if that was all. But it goes further and says that “the next time someone says we can’t question their judgment on guns or whatever, show them this image.” That logic—or lack thereof, it’s an ad hominem—can be used to put all of our founding principles on the chopping block. It’s an attempt to delegitimize the animating principles of our country.
What I don't get is this newfound attempt to argue that what we once called the Great Experiment is immune from criticism, to portray the success of America as an inevitable result of the holy prophets who gave us the Constitution on stone tablets and not the work of men who made mistakes and learned from them.