See the video of San Diego trans boy, 6, that has exploded in popularity and vexed critics

A family's video detailing their 6-year-old trans son's declaration of his male gender has gone viral and sparked fierce debate about the nature of gender and identity in our society and the changing beliefs around those topics.

Wisconsin's WAOW Channel 9 reported that the video story of Ryland Wittington, whose family lives in San Diego, CA, received millions of views in its first days on YouTube.

Jeff and Hillary Wittington's baby Ryland announced as soon as he could speak that he was not a girl, but a boy. He insisted on being referred to as his sister's brother and, after conferring with psychiatric professionals, the Wittingtons allowed Ryland to express his gender as male at the age of 5.

"I'm a transgender kid," said Ryland in the video. "I'm the happiest I've ever been in my whole life. Thank you to my parents."

"With phases they just come and go or kids try things on for a little while," said San Diego-based gender therapist Darlene Tando to ABC News. "But with gender identity, when a child is transgender, typically nothing fades in or out. It just really stays the same for a long time."

Some reactions to the video, however, have been hostile.

"I would NEVER do this to my CHILD," wrote one People magazine reader after the publication ran a story about Ryland.

Experts like Tando, however, say that allowing trans kids to express their gender is the best thing for them.

"There's huge benefits to doing this earlier in life," Tando said. "It's like they've been given this gift where everyone around them recognizes them for who they really are."

Watch video about this story, embedded below:

Watch the Wittington family's original video: