How To Argue Rightly?

tODD raises an important point. In case you missed his comment on the “Why the Vitriol?” post, he says, among other things,

Dr. Veith, it’s good for you to call out the “knee-jerk HATE” that
some liberals have leveled at Palin. However, your entry seems to have
ignored the knee-jerk hate that some here on your own site spread
about Democrats.

OK, so where should Christians–enjoined to love even their enemies, obey the 8th commandment (the one about False Witness, for those who number differently), and “put the best construction on everything” (as Luther’s “Small Catechism” puts it in the explanation to that commandment)–draw the line in their discourse?

An argument is meant to persuade, but when it degenerates into merely attacking the opponent, the opponent becomes defensive and so will never let you persuade him. Thus, besides being ethically problematic, that approach is just ineffective arguing.

I also think there is a difference between complaining in the abstract–against a distant opponent, addressing someone who already agrees with you–and addressing a “neighbor,” an actual person who holds that belief you oppose. In the former case, one is free to rant and rave, which is why blog discussions can get so overheated; but in the latter case, we must argue vocationally, that is, in love and service to our neighbor.

What other principles ought we all to consider? What is fair game and what is out of bounds?