Affleck will play Batman in the Man of Steel sequel, bringing together the superheroes on film for the first time.
Appearing on Jimmy Fallon's US talk show, Affleck said Warner Bros. warned him there could be a cold response.
"I'm a big boy. If I can handle an Emmy snub, I can handle anything," the 41-year-old joked.
Affleck, who won an Oscar this year for directing the hostage thriller Argo, has been criticised by some fans of the caped crusader who disagree with the decision to cast him as one of DC Comics' most enduringly popular characters, opposite Henry Cavill as Superman.
A petition on Change.org urging Warner Bros. to "Remove Ben Affleck as Batman/Bruce Wayne in the Superman/Batman movie" has gathered more than 93,000 signatures since it was started.
Affleck will play an older version of the character in the film directed by Man of Steel's Zack Snyder.
The actor told Fallon: "The people from the studio said, 'We want to talk to you because people go through this process and it can be a little trying'.
"They said, 'We want to show you some of the reactions that past cast members have got on the internet'."
He continued: "I saw the announcement, I look at the first comment and it's like, 'Ben Affleck is going to be Batman' and the first one goes, 'Noooooooo!'
Affleck admitted he was sceptical about taking the role when Warner Bros first offered it to him.
"I thought, 'I'm not 25 man and are you sure about this?' And they said, 'Come down we want to show you what we're doing,' and it was incredible.
"Zack [Snyder] had this incredible take on it. Obviously you can't do what Christian [Bale] did. Those movies are awesome, amazing, so he [Snyder] wants to do something different but still in keeping with [previous films] so I thought, 'This is a brilliant way to do this, I really know how to hook into this'."
The film is expected to be released in the summer of 2015.
Ben Affleck has shrugged off negative reactions after being cast as Batman in a new film opposite Superman, saying he's a "big boy" who "can handle" it.