BULL DOG EVANGELIZATION?
I remember this scene from Jack London's book, White Fang. These guys were hosting a series of dog fights in which White Fang was forced to participate. In his last fight they set the poor wolf up against a small bulldog. The bulldog quickly attached himself to White Fang's neck, and began to slowly suffocate the life out of the hero of the novel. Calmly, cooly, the bulldog knew he would win as he deprived his opponent of air. Only a chance passer-by put an end to the shenanigans, allowing White Fang to carry on with life.
Having participated in some comboxing (discussions in a combox), one gets the sense that combox evangelization can learn something from that bulldog. You don't need to act exciteable, talk big, or be in any way inflammatory. All you do is draw the opponenet out and get him to reveal his soft spot, then you move in and attack his argument's weaknesses relentlessly.
ALTERNATIVE TO EVANGELICAL NARCISSISM
After all, the ultimate goal of combox evangelization is the onlookers. You aren't trying to get your opponent to hang his head, or throw in the towel. The fence-sitting lurkers are the prize, those who read but don't necessarily participate. It's these fence-sitters you are arguing for, not the entrenched opposition. You need to attract the undecided.
As you evangelize via the combox, you should never throw the book at your opponent. You should never publish "may God have mercy on your soul," just think it in your head. After all, barking only ever scares people away, and it does little to move the conversation or the heart of the reader anywhere. It turns off onlookers to your explanation of reality because you just look like a hysterical troll, and everyone walks away feeling like they gained nothing. Everyone except maybe your followers.
Honestly, the only thing belligerent, inflammatory, hard nosed rhetoric does is keep your groupies interested in being your groupie. Preaching-to-the-choir evangelization = evangelical narcissism. If you're more interested in only presenting how you the commenter are right rather than meeting the opponent where he is (i.e. where he's wrong), you'll lose the undecided. The goal is ultimately to lead to Truth, not drag, or push.
COME, FOLLOW ME!
Does this mean compromise on Truth, or water it down? Hell no! But there are real ways to hold a conversation where you share Truth, demonstrate it, and discover it, and remain friends with your opponent to the end. It involves professionalism, patience, and earnest engagement with your opponents ideas, rather than your own.
Remember, preaching to the choir is not the point, you want to attract the undecided through charitable discussion, and a clear dismantling of the opponents ideas. You need to draw your opponent out of his lair of anti-Catholicism, and anti-life jingos, and into the realm of rational argument. The only way to do that is by showing an interest in what and how your opponent thinks.
The more interest you have in how your opponent thinks, reasons, and views the world, the clearer, and more helpful he'll be, and the more effective your discussion will turn out. If you are patient, avoid ad hominem, and engage the other's ideas charitably and with clarity, you will be able to cover more ground, and provide more fuel for thought for both your opponent, and the lurkers on the blog.
Instead of everyone reading catchy cliches of why Catholicism is stupid, now everyone gets to read and question the opponents beliefs. Every reader gets the opportunity to question the logic of your opponent's arguments. This focusing on dismantling the opponent's beliefs will give you the upper hand. Put the burden of proof on his shoulders, and once enough evidence and reason is weighed against him, his argument will naturally collapse.
I call this bulldog evangelism because you sink your teeth into the opponent's weaknesses, and hold on with relentless, patient, methodical questioning. You're turning his weakness, his vulnerability, into your strength. His beliefs, and the arguments he throws out there in the combox now become more of a lesson in fallacy, rather than an appealing subterfuge, to those undecided lurkers.