What reasons does Atticus give the children not to play the Boo Radley game?

Atticus tells the children to stop tormenting Boo, and he lectures them about how Boo has a right to his privacy, and that they shouldn't go near the house unless they're invited. He accuses them of putting Boo's life history on display for the edification of the neighborhood. Jem says that he didn't say they were doing that, and thus inadvertently admits that they were doing just that. Atticus caught him with "the oldest lawyer's trick on record."