I thought it was a reasonable question from someone considered by most people to be completely insane. Even insanity deserves to be treated politely. I've been thinking about his question and I think I've got one answer. We are so rude because that's how we hear right wing radio hosts talk, that how we hear cable news folk talk and, yes, that's how we hear nationally known political figures talk. Civil discourse has apparently died a quiet and unnoticed death.
Like Lazarus, though, that death can be undone. We just need to figure out how to do it.