In Chapter 5 of the novel To Kill a Mockingbird, why does Miss Maudie say that Scout is being morbid?

In Chapter 5, Scout asks Miss Maudie if Boo Radley is still alive. Miss Maudie says, "What a morbid question. But I suppose it's a morbid subject." (Lee 57) Miss Maudie tells Scout that she knows Arthur "Boo" Radley is still alive because she hasn't seen him carried out of his house yet. Scout suggest that maybe Boo died, and they stuffed him up the chimney. Miss Maudie continues to tell Scout details about the Radley family. She says that Mr. Radley was a "foot-washing Baptist" who felt that any type of pleasurable activity was a sin. The Radleys rarely left their house, but when Arthur was a boy, he always spoke kindly to Miss Maudie. Nobody really knows what goes on behind the Radleys' closed doors, and Miss Maudie says that if Boo wasn't crazy before, he probably is now.