Elon Musk is newly minted as humanity’s first trillionaire, but the world’s richest man seems grumpy. And he definitely is not a fan of mine.

“Kristof is lying through his teeth,” he announced on social media this week.

I got on his nerves for pushing back at his claims that his demolition of the United States Agency for International Development last year did not cost lives. The fracas began after Representative Ro Khanna, a California Democrat, said that Musk had “possibly sentenced to death” a large number of children, and Musk retorted that it was “time to sue this liar.”

“There is not even a single dead child!” Musk protested on social media. I noted that I had met many families of children who had died — and that’s when he concluded that I was lying.

Musk’s assertion that not a single child died is absurd, yet he doubled down: “They cannot cite a single name of someone who died out of the ‘millions’ they falsely claim have died. Not a single name!”

On X, I began to give Musk some names. Let me elaborate:

Jibia was a 10-year-old girl, ranking third out of 58 students in her fourth-grade class in Rwamwanja, Uganda. Aid cuts meant that the local clinic ran out of $2 bed nets to protect from mosquitoes, as well as anti-malaria medicines. Jibia died of malaria last July, her mother told me outside the family home. Medical records confirmed that, and health workers told me that she would have been fine without the aid cuts: Replacing her tattered bed net with a new one could have prevented malaria, and in any case drugs would have helped her to recover promptly.

Yamah Freeman hemorrhaged while pregnant with her third child in her village in Liberia. The United States had provided ambulances to the local hospital, but the aid cuts under Musk and President Trump meant that the ambulances had no fuel. The strongest young men in the village placed her on their shoulders and raced down the path toward town, shouting encouragement to her as they ran, but she bled to death along the way. Her parents and sister told me about this, and I visited her grave.

Achol Deng, 8, had been infected with H.I.V. at birth in South Sudan but had been kept alive by American-provided medicines costing just 12 cents a day. The dismantling of U.S.A.I.D. and the resulting chaos meant that she lost her caseworker and access to medicines, and soon died of an opportunistic infection, health workers told me.

I could keep going. A Boston University researcher estimated that the aid cuts have cost more than 750,000 lives worldwide. A study published in the Lancet, the British medical journal, forecast that at present rates, the aid defunding will cost 9.4 million lives by 2030.

These figures may not be accurate; we just don’t have solid mortality data, and the aid cuts have also reduced data collection. What I can say after visiting numerous impoverished villages is that aid cuts are unquestionably costing the lives of many children.

Some prominent conservatives leaped to the defense of Musk, saying in effect: Why is it our job to save the lives of children in South Sudan? Why don’t rich liberals write checks? Why don’t other countries do more?

Those are fair questions. But if any of us came across an ambulance that had run out of gas with a hemorrhaging woman inside, surely we would happily hand over a $10 bill to save her life.

Until Trump’s second term, American aid cost just 23 cents for every $100 of gross national income and saved a life approximately once every 10 seconds. Seems like a bargain to me. Certainly it appears wiser than spending billions of dollars on a war with Iran.

I say “wiser” because all this is not just about compassion but also about self-interest. Aid money serves national security and protects us from diseases. I’ve noted that the current Ebola outbreak in Africa may have gotten out of control precisely because we cut aid spending in the region.

Yes, other countries should do more, impoverished countries should be less corrupt, and our own aid can be allocated more wisely. But note that some countries in Europe are significantly more generous than America, spending up to 10 times as much on aid as a share of national income as we do.

Should liberals donate more to humanitarian causes? Sure. But compassion isn’t a liberal impulse — it’s a human one. It was evangelicals and Republicans who in 2003 started the single best aid program ever, the President’s Emergency Plan for AIDS Relief, or PEPFAR; it has saved more than 26 million lives so far. Some of the most heroic aid workers I’ve met in dangerous locations have been Christian missionaries, from nuns to doctors; they would dispute the idea that empathy is woke.

It’s reasonable to ask how much we should spend or how we should reform the system. But why would anyone begrudge $2 bed nets or $4 malaria vaccines to save children’s lives?

So let me offer a challenge to Musk: Come with me on a reporting trip to South Sudan or Somalia or Mozambique. Meet starving children whose lives can be easily saved. Hold them. Look into their eyes. Talk to their terrified moms.

You’ll understand that these kids are just like ours, except that they didn’t do as well in the lottery of birth — and that just because we can’t save every child’s life doesn’t mean we should save none of them.