'I wont have it.'

When Atticus says this line, he is thinking only not of his children, but of Mr. Radley.  He doesn't want the case to be hidden as he believes that it shows that Jem did kill Mr. Ewell.  He also believes that if it is hidden, it will teach Jem that things can be covered up.  He believes that Jem killed Mr. Ewell, he wants him to stand trial.  He is ignoring what Mr. tate is saying  about Scout not fully understanding what happened. From Mr. Tates previous statement, Atticus believes that he is trying to shift the blame from Jem to Mr. Radley.