The US president has appeared onstage with a school student, saying the child was forced to read My Shadow Is Pink by Australian author and illustrator Scott Stuart.
The book is about a boy who loves "things not for boys" such as princesses and fairies.
The rhyming tale challenges gender stereotypes and is part of a best-selling series.
Trump introduced the 12-year-old student, who stood on a riser at a Religious Liberty Commission event to deliver a short speech.
When he was in fifth grade in 2024, he was forced to teach his kindergarten buddy about changing genders by reading the book aloud, and he was afraid when his family spoke up about it, the boy said.
"The school treated us badly, and kids started bullying me and my brother because of our faith, and the school did nothing to stop it," he said.
"I believe kids like me should be able to live our faith at school without being forced to go against what we believe. I hope no other family has to go through what mine did."
Stuart has responded in an online video, saying Trump is using his children's books to further his own political agenda, and the student who made the speech was being used as a pawn.
"The irony here is that they want acceptance for their beliefs, but not to extend that acceptance onto others," the author said.
The My Shadow books are not about culture wars, but about helping kids be themselves without prejudice, according to Stuart, who also said his inbox had been filled with messages of hate since the speech.In January, the Malaysian government banned another book from the series, My Shadow is Purple, stating it "may be harmful to morals".
The story is about a child who does not identify as either a boy or a girl, with the story using colours as a means to discuss not conforming to gender expectations.
"My Dad has a shadow that's blue as a berry, and my Mum's is as pink as a blossoming cherry," it reads.
"There's only those choices, a 2 or a 1. But mine is quite different, it's both and it's none."
The book was published in 2022, and a teacher in the southern US state of Georgia was fired the following year for reading it to her fifth-grade students.
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