If you know who Sean Hannity is, you probably know that he is no fan of the Green New Deal. The proposal has blanketed Fox News since it debuted in November 2018, with Hannity and fellow hosts on the network narrowing in a particular line of attack, summarized during a radio spot he did last year: “What they are proposing is so outrageously expensive and cost prohibitive even they acknowledge that if we confiscated all the billionaires’ wealth, it still wouldn’t be able to pay for this mess of theirs.” Along similar lines, Republicans circulated a bogus study from the industry-funded American Action Forum claiming a Green New Deal would cost $93tn, elevating the number into something of a meme among rightwing talking heads and politicians. Senate majority leader Mitch McConnell told his colleagues it would be more than enough to “buy every American a Ferrari”.

Hannity and McConnell, along with most of the rest of the Republican party, have more recently been heaping praise onto Trump for assassinating Iranian Gen Qassem Suleimani. “This is a huge victory for American intelligence, a huge victory for our military, a huge victory for the state department, and a huge victory and total leadership by the president,” Hannity boasted after the killing. Without consulting Congress, the president kicked long-simmering US-Iran tensions up to a boil that now threatens to spill over into another full-blown war in the Middle East. His threats to bomb cultural sites throughout the country – in violation of international law – make that even more likely. So why aren’t Republicans asking how the government would pay for it?

A recent study from Brown University’s Watson Institute found that, since 2001, wars in Afghanistan, Syria and Pakistan have cost the US $6.4tn – $2tn more than all federal spending in 2018. The trouble with a prospective new war in Iran, of course, isn’t that it would cost too much money. It’s that it would put potentially millions of lives at risk, mostly to appease Donald Trump’s fragile ego, a coterie of neocons who’ve been edging toward it for years and a slew of defense contractors eager to cash in. Neither a Green New Deal nor another war would plummet the US into bankruptcy, a virtual impossibility barring earth-shattering changes to the make-up global economy. They probably wouldn’t even raise inflation.

The disconnect between Republicans’ fiscal conservatism on climate and spendthrift war drums illustrates a basic fact about American politics: that our budgets are more than anything expressions of what it is the country chooses to value – not how much money we have in the bank. The only time costs become an issue is when it comes to programs that run counter to Republican policy priorities, whether by making sure that everyone has healthcare or taking on the urgent threat of the climate crisis, the potential real costs of which are virtually exponential.

In office, Republicans have been prolific deficit spenders, from supposed small-government ideologue Ronald Reagan to George W Bush to Trump, who pushed through $2tn worth of tax cuts for the wealthy. Democrats all too often fall into the trap of worrying about the deficit, from the Clinton administration’s war on public programs to Nancy Pelosi’s seemingly religious commitment to enforcing so-called pay-as-you-go (“Paygo”) rules that would kneecap any progressive agenda. At the same time, the establishment Democrats urging fiscal prudence and (rightfully) calling Trump an illegitimate president have reliably voted to expand his military budget, arming him with $738bn for this year alone.

At this point, nobody is expecting intellectual honesty from the Republican party. Democrats, though, shouldn’t play into their hands. It’s time to be as hawkish about taking on real threats as Republicans are about taking on fake ones, whatever the cost.

• Kate Aronoff is a writer based in New York