How does a liberal know that her open-borders arguments are a bust? When even David Frum — David Frum! — has to step in.

On the Monday edition Ari Melber's MSNBC show The Beat, New York Times editorial board member Mara Gay made a two-pronged argument in favor of allowing countless Central Americans to enter the US: One, violence is rampant in those countries; and two, in any case, people should be admitted who are fleeing "domestic violence."

First, she claimed that "the reason that many of these people, these migrants, are coming to the United States is that because they are desperate, and that they are fleeing incredible, you know, incredibly violent experiences, whether through domestic violence or just the lawlessness in some of Central America."

Frum eviscerated both arguments. First, he pointed out that — contrary to Gay's claim of unchecked violence — the homicide rate in Central America has actually declined by two-thirds since 2011 and thus "the rate of migration has nothing to do with levels of violence in Central America."

Likely stunned by this rare disagreement among panelists for an MSNBC primetime show (let alone any show), Melber jumped in and allowed Gay to push back and rule that illegal immigrants "want a better life and that many of them are fleeing violent situations. Whether that be gangs, or just violence in their own families and a failure of their own states to protect them from it."

Appearing to admit defeat, Gay retreated by snidely stating that "there’s no reason to litigate this, really, and there is nothing wrong historically with the United States of America welcoming refugees and immigrants to our shores."

Translation: forget those pesky facts. Just open the darn borders!

Before pivoting back to their regularly-scheduled Trump-bashing, Frum concluded (emphasis mine):

The asylum system is not supposed to be a response to troubling people in societies. It’s a response to persecution. That is, the authorities are coming for you. There's something — because of something you can’t control, that’s a benign personal characteristic, your state is persecuting you. That’s what asylum is for. It's not a -- that’s not how you solve the problems of the world and to go back to the President, I mean, the President sent very tough, fierce messages in 2017, and indeed he reduced the flows of migration through growling.

Here's the transcript.