How does Atticus' refusal to avoid a trial for Jem show about his character?

Atticus is a very rules oriented person. He will not accept a lie, even if it involves his kids. In the end Heck Tate is able to convince Atticus that a trial would do nobody any good. A trial would hurt Jem and certainly destroy Boo, the man who saved his kids. Atticus finally concedes that, in this case, the truth would do too much harm.