In her post, Larson called being cast as Captain Marvel a "trust fall into the internet."

"I know who I am, but it's wild how quickly you can forget once someone calls you something terrible. I was reminded how the acceptance of community is a deeply rooted need — but I don't want to live worried people will hate me because I'm myself!" Larson wrote. "We should all have the freedom to be our authentic selves without fear or judgment. It's scary to chip away at all the hardness we coat ourselves with to protect that perfect little being inside. Yeah, people can be mean, but they can also be so many other wonderful things too. Let's make this place a safe space. No hate and more understanding. To the followers that are new: welcome!"

There has been a long history of knee jerk reactions to comic book casting announcements dating back to 1988, when grumbles about Mister Mom star Michael Keaton being casted as Batman were heard in comic book stores all over the country. But in the online age, reactions can be particularly harsh on women, with Wonder Woman star Gal Gadot facing body shaming issues following her casting, with some online complaining she was too skinny to play the Amazonian warrior. Her response? "Wonder Woman is a one-breasted Greek Amazonian woman, so if I were to really go 'by the book' — that would be a problem."

In Captain Marvel, Larson will play Carol Danvers, who in the comics is a test pilot who gains superpowers after an encounter with aliens.

Kelly Sue Deconnick , the comic book writer who revamped Captain Marvel into her current comic's incarnation, came out in support of Larson’s casting.

“My dream casting — or the actor who is the voice in my head — is Kathleen Turner from about 1983. She could be both sexy and awkward and powerful. She could do all of those things at once. From what I can tell, Brie Larson can do those things too," Kelly Sue DeConnick said in an interview with Vanity Fair. "She has a gravitas and she has a power to her. But you can see she also has a sense of humor and playfulness there. I’m psyched.”

Marvel Studios' Captain Marvel will be released in 2019.