Chesley Sullenberger, the pilot who performed the “Miracle on the Hudson”, has told Donald Trump’s daughter-in-law Lara Trump to “grow up” and “show some decency”, after she mocked Joe Biden for stuttering.

Biden, a frontrunner for the Democratic nomination to face President Trump in November, has spoken openly about his lifelong experiences with a stutter.

Lara Trump, who is married to the president’s second son Eric, works for the Trump re-election campaign and spoke in that capacity at an event in Iowa on Friday, the day after the seventh Democratic debate.

“I feel kind of sad for Biden,” she said. “And you know that’s when it’s not going well for him, right, because I’m supposed to want him to fail at every turn. But every time he comes onstage or they turn to him, I’m like, ‘Joe, can you get it out? Let’s get the words out, Joe.’”

Trump is not the first prominent supporter of her father-in-law to face criticism for mocking Biden’s stutter: Fox News has aired montages of his stuttering on the debate stage and former White House press secretary Sarah Sanders deleted a mocking tweet in December.

Nonetheless, on Friday Trump criticised reporting of her remarks and insisted in a tweet that “anyone who takes 10 seconds to watch what I actually said can clearly see that I never mention a stutter – didn’t even know he had one”.

Here’s @LaraLeaTrump at Trump event in Iowa mocking Biden for stuttering: "I feel kind of sad for Biden ... I'm supposed to want him to fail at every turn, but every time they turn to him I'm like, 'Joe can you get it out? Let's get the words out Joe.’” pic.twitter.com/0inN9wXYJF — Aaron Rupar (@atrupar) January 17, 2020

On Saturday, a well-known voice fired back. Sullenberger, known as “Sully”, became famous in January 2009 after his airliner struck a flock of Canada geese but he managed to land it on the Hudson river, saving the lives of all 155 people onboard. In 2016, Clint Eastwood made the story into a film with Tom Hanks in the eponymous title role.

In a column for the New York Times, Sullenberger began by remembering his own experiences with a stutter in his childhood in Texas, “the anguish of being called on in grade school, knowing that I was going to have a hard time getting the words out; that my words could not keep up with my mind, and they would often come out jumbled”.

“My neck and face would quickly begin to flush a bright red,” he wrote, “the searing heat rising all the way to the top of my head; every eye in the room on me; the intense and painful humiliation, and bullying that would follow, all because of my inability to get the words out.

“Those feelings came rushing back, when I heard Lara Trump mocking former Vice-President Joe Biden at a Trump campaign event, with the very words that caused my childhood agony.”

Sullenberger disclosed that he attended a Biden fundraiser last year, but said: “This issue goes beyond politics.”

“Regardless of how you feel about Joe Biden,” he wrote, “or his chances of becoming the Democratic nominee for president; whether you are a Republican, a Democrat, or none of the above; whether you stuttered as a child or laughed at one who did; whether as a parent you try to protect your own stuttering child from taunts such as those made by the president’s daughter-in-law; these words come without hesitation: Stop. Grow up. Show some decency. People who can’t have no place in public life.”

Trump’s words, he said, were indicative of a “culture of cruelty” which “drives decent people from public service and … makes millions of Americans recoil from politics, and even from participating in our democracy”.

“Vice-President Biden has spoken openly – and courageously, in my view – about the pain of his severe childhood stutter,” Sullenberger wrote. “He takes time to reach out to children who have suffered as he did.

“So, to every child who feels today, what I felt, after hearing those cruel remarks by an adult who should know better, here is what I want you to know: “You are fine, just as you are.”

Sullenberger concluded by saying “a speech disorder is a lot easier to treat than a character defect” and telling any children reading to “ignore kids (and adults) who are mean, or don’t know what it feels like to stutter.

“Respond by showing them how to be kind, polite, respectful and generous, to be brave enough to try big things, even though you are not perfect.”

In a tweet on Sunday, Biden thanked Sullenberger for “sharing your story. There’s a lot of kids who I bet needed to hear it. Being different isn’t a barrier to success. It can give you the strength to save lives in a crash landing – or even run for president.”