The funnyman has refused to take part in a publicity campaign for the film, in which he plays a vigilante named Colonel Stars and Stripes, as he felt he could no longer support the project following a school shooting in Connecticut last year (12).
Carrey cited the movie's "level of violence" for his decision, but 16-year-old Moretz, who plays a costumed assassin in the movie, insists his fears are misguided.
She tells Britain's The Sun, "It's a movie. If you are going to believe and be affected by an action film, you shouldn't go to see Pocahontas because you are going to think you are a Disney princess.
"If you are that easily swayed, you might see The Silence of the Lambs and think you are a serial killer. It's a movie and it's fake, and I've known that since I was a kid... I don't want to run around trying to kill people and cuss. If anything, these movies teach you what not to do."
She adds of Carrey, "Each to their own. I know the movie I made and it's all good and I respect his decision."
A young gunman killed 20 children and six adults at Connecticut's Sandy Hook Elementary School in December (12), sparking a fevered debate in America over weapons laws and whether violent movies influence the behaviour of disturbed individuals.