(CNN) Donald Trump supporter Ben Carson compared a transgender person to someone who wakes up one morning and decides he or she is Afghan after watching a movie or reading books about Afghanistan.

"For thousands of years, mankind has known what a man is and what a woman is," Carson said to applause Tuesday at the Florida delegation breakfast near the Republican National Convention in Cleveland. "And now all of a sudden we don't know anymore. Now, is that the height of absurdity? Because today you feel like a woman, even though everything about you genetically says that you're a man or vice versa?"

"Wouldn't that be the same as if you woke up tomorrow morning after seeing a movie about Afghanistan or reading some books and said, 'You know what? I'm Afghanistan. I know I don't look that way. My ancestors came from Sweden, or something, I don't know. But I really am. And if you say I'm not, (then) you're racist,'" the former presidential candidate continued.

The retired neurosurgeon, who has proposed separate bathrooms for transgender people, has made controversial statements about LGBT issues in the past.

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The Obama administration issued guidance in May directing public schools to allow transgender students to use bathrooms matching their gender identity.

A joint letter from the Departments of Education and Justice went to schools with guidelines to ensure that "transgender students enjoy a supportive and nondiscriminatory school environment," the Obama administration said.

Carson said he's "disturbed" that "secular progressives" are trying to make transgender issues a "civil rights issue."

"Anytime the secular progressives want to get people on their side, they go back to the civil rights movement, and they say this is a civil rights issue and it's not a civil rights issue," he said. "But we have to be willing to stand up, we have to be willing to call out people for this absolutely ridiculous stuff that they're trying to put over on us, that they're trying to put over on our children."