When it was first announced in 2016 that actor Matt Bomer was going to play a transgender woman in a film produced by Mark Ruffalo, there was some outrage — but there were also people who didn't quite understand the problem.

In a twitter thread, actress and advocate Jen Richards explained why the "it's just acting" argument doesn't hold up — and is actually harmful to trans women.

The explanation from Richards, who is trans herself, was prompted by a tweet from Deadline Hollywood proclaiming, ".@MattBomer plays a transgender woman who falls in love with a straight man in 'Anything' ..."

As Richards notes, trans women aren't wearing a costume, and to cast a cis man as a trans woman suggests that they are.

"I auditioned for this," she explained in the linked tweet. "I told them they shouldn't have a cis man play a trans woman. They didn't care."

"More importantly," she adds to the thread, "read this for real life consequences of exacerbating cultural belief that trans women are men."

The article she links is a piece she wrote for NewNowNext by Logo, titled "Why Straight Men Kill The Trans Women They Love," which was published in May. In the article, Richards writes about Mercedes Williamson, "a 17-year old trans girl living in Alabama" who was murdered by a man she was dating, Joshua Vallum, when he learned she was transgender.

"Vallum was a member of the Latin Kings, which forbids homosexual acts, and he was afraid word would get out," Richards wrote. "It’s a particularly tragic story because it all hinges on the belief that a man having sex with a trans woman is a homosexual act."

The killing of a transgender woman is sadly not an isolated incident. Newsweek reported in March "Seven transgender women were killed in the first six weeks of 2017, putting the rate well on course to beat the previous figure of 23 reported murders last year."

So by continuing to cast men as trans women, Hollywood is furthering the notion that trans women are not women, and that a cis man who dates a trans woman is actually gay. It's a dangerous misconception to spread.

Richards further highlights this issue in her tweets with photos of actors who play trans women on and off set.

Jen Richards/Twitter - twitter.com

Jen Richards/Twitter - twitter.com

Again, by not hiring trans women to play trans women, it perpetuates the idea that trans women are simply men in drag. And it also pushes another stereotype:

Still, Richards remains hopeful that the circle will be broken eventually. "It's coming," she tweeted. "I've seen enormous change in Hollywood over last few years."