As Affleck recalled being told by the studio executives, “‘Listen, we want to talk to you because people go through this process and … it can be trying.’ I said, ‘What do you mean?’ ‘We want to show you some of the reactions that past people who have been cast have gotten, like on the Internet and stuff.'”
He didn’t get into details about what actors were on the receiving end of those armchair comments, but he did note that the reactions were for “people who were in these movies who did a great job, and (the commenters) were like, ‘Kill him!’ … You can’t say it before the movie comes out. It doesn’t matter what you think then, it matters what you think when you see the movie.”
Source: NBC Today Show