LOL
Actually, as long as the differences in doctrine are the mark of the conversation, I'm perfectly capable of having a polite discussion with them.
When the talk descends to the level of "the pope is the anti-Christ," "Jesuits were the ones that created Islam," "tunnels underneath the convent are filled with the rotting corpses of aborted fetuses," "Catholics tried for 1500 years to destroy the Bible," and so on, that's when I break out the Chick cartoon.
Otherwise, I actually rather enjoy discussing the differences in doctrine. I sort of figure it being a Proverbs 27:17 opportunity. Just as long as it stays polite.
Unfortunately, particularly in recent months, it seems like that is not too possible around these parts.