Jill Filipovic is a journalist based in Washington and author of the book, "The H-Spot: The Feminist Pursuit of Happiness." Follow her on Twitter. The opinions expressed in this commentary are solely her own. View more opinion articles on CNN.

(CNN) President Donald Trump may have finally met his match: The Squad.

The famously foul-mouthed President on Sunday launched yet another Twitter tirade , saying that the four congresswomen, known as The Squad -- US Reps. Ilhan Omar, Ayanna Pressley, Alexandria Ocasio-Cortez and Rashida Tlaib -- should "go back" to the countries they came from. All four are US citizens, and three were born in the United States (Omar is a refugee from Somalia who spent part of her life in a Kenyan refugee camp).

Jill Filipovic

But the women haven't backed down. Nor have they responded with platitudes or undeserved tact. Instead, they've called the President what he is ("racist") and his language what it is ("white nationalist"). Unlike the many politicians and public figures previously attacked by Trump, these four women can fight him on his own turf: Ocasio-Cortez, in particular, is social media savvy and understands the particular patois of Twitter. They also have youth on their side; next to them, Trump seems like the grumpy, racist grandpa that he is.

And, more importantly, they have the moral high ground. It takes some real mental jiujitsu to twist Trump's comments into anything other than straight-up racism. How else do you explain someone telling four American citizens to "go back" to foreign countries? What the President really means is that nonwhite Americans have a less legitimate claim on this nation than white ones. Two of the President's three wives, after all, have been immigrants themselves, and he doesn't seem to suggest that they should "go back."

The "go back" assault is fundamentally racist and cruel. It's more the language you expect to hear being hurled during the commission of a hate crime, not by the President of the United States. It is a way to harass not just immigrants but any nonwhite person in America. And it belies the fundamental truth about this nation -- that the vast majority of us are immigrants or descended from them. Those who have a native claim to this land are not white, and yet racist leaders like Trump make clear that they believe white America is "real" America.

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