The book explores the biological, psychological, and philosophical areas of the transgender debate. It received positive reviews by professors of psychiatry, psychology, and medical ethics at universities such as Johns Hopkins, Boston University, New York University, and Columbia University.
On Monday, a spokesperson for Amazon declined to comment on Anderson's claims.
Under the company's content guidelines, Amazon prohibits material which "we determine is hate speech" or is "inappropriate or offensive."
Amazon also states that it will inform the "author, publisher, or selling partner" if their material is removed from the site, and would allow them a chance to appeal the removal. However, Anderson told CNA on Monday that he had received no explanation for his book's removal.
Dr. Robert George, a Princeton University law professor, called the removal of Anderson's book "the new Woke religion's Index of Prohibited Books."
The legal group Alliance Defending Freedom (ADF) stated "Robust debate and dialogue require that all viewpoints be heard. So why did Amazon remove 'When Harry Became Sally'?"
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The incident comes after the Equality Act was introduced in Congress last week. The legislation would create protected classes for sexual orientation and gender identity. Anderson and others have warned that the law would create sweeping changes in society, requiring people to acknowledge gender ideology and allow people access to sex-specific locker rooms and bathrooms based on their gender identity and not their biological sex.
"Make no mistake, both Big Government and Big Tech can undermine human dignity and liberty, human flourishing and the common good," Anderson stated on Monday.