Image copyright Kristi Merritt / Facebook

Meet Kristi Merritt, from Washington in the US.

She's posed for a string of photographs that compare dressing up as a Mexican, or a pirate, to being transgender.

More than 70,000 people have shared the images that Merritt posted to Facebook, and more than thirty thousand have hit the like button. But many are unhappy about the comparison, and it's triggered a slew of negative articles online as well.

The caption accompanying the pictures reads: "A man in women's clothes does not make him a woman. Men should not get to be in our bathrooms or lockers!" which explains Merritt's bone of contention.

It's the battle over what have been dubbed "bathroom bills".

Some argue that allowing transgender women to use facilities designated for women will protect their dignity and safety. But others - Merritt included - make the point that it could offer a loophole to male sexual predators who want to gain access to female only spaces.

Across the US there is a complex patchwork of laws governing which public toilets transgender people can use. In some places they can choose whichever they feel they identify with - men's or women's. In others, they are forced to use the one that matches their biological sex. Federal laws clash with state laws, which may themselves overrule local government decisions. The matter is far from settled - in North Carolina an ordinance was recently rolled back, so transgender people who had been able to choose must now use the bathroom that corresponds with their biology.

Image copyright Kristi Merritt / Facebook

Image copyright Kristi Merritt / Facebook Image caption Merritt also dressed up as American football star Russell Wilson

Messages on the post were limited to Merritt's friends and were mostly sympathetic. "This is not hate speech, this is basic common sense," and "seems to me she has a point," wrote two users. Not all of her friends agreed, however. "These posts are PURE ignorance. Please keep your hate to yourself. It's just a bathroom!" wrote another.

Some Facebook users started sending abusive messages to Merritt, which she reposted under the photographs. "Your kind are at an end. Fear me... I am coming," read one of the messages. Others reported the posts to Facebook for containing nudity, in an apparent attempt to have them removed from the site, although they still appear at the time of writing.

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Pro-transgender rights campaigners have seen social media posts about the issue go viral on numerous occasions. Last year Michael C. Hughes, a transgender man, posted this image to Twitter, which was shared more than 4,000 times.

Image copyright @_michaelhughes1 / Twitter

Hughes told BBC Trending he thought Merritt was "coming from a place of ignorance". In addition to his view that transgender people had a basic right to use the bathroom they identified with, he says efforts to legislate against that could actually prove dangerous.

"Not for myself, I'm 6 feet tall so it's the women who would be afraid of me. The real safety issue comes for transgender women being forced into men's facilities."

We have asked Merritt for comment but not yet heard back.

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