When, in email or conversation, you find a correspondent who isn't arguing well, who uses fallacies or other attempts to short-circuit you, who simply won't talk turkey, don't get mad and flame the bastard. Get polite. Ask them to PrettyPlease explain their position. Don't overdo it - sarcasm is worse than flames - but just jolly them along. This is a lot more likely to further the conversation than returning fire with fire. 

See also StampOutFires.