In the comments section of another post, St. Martel observes that:
Discussion fora on the Internet do have a tendency to make people a little less polite than they would be in person. Not sure why that is...
[May I point out how glad I am that my readers are capable of noticing this and correcting for tone on their own? Yes, I may? Okay, I will then.]
I think there are 3 main reasons why internet discussions are less polite:
1) Anonymity. People feel free to say things they wouldn't otherwise say when it can't be traced back to their "real" identity, so that there are no consequences (for those with limited capacity to feel guilt, anyway).
While this probably accounts for many of the worst abusers, I don't think it's all that relevant in the case of a) people like myself who blog under our real names, or b) people with robust consciences who don't like trolling and insulting people so much.
2) Lack of bodily interaction. We human beings consist of both bodies and souls. When we have conversations face-to-face, we aren't just communicating with words. Our social instincts, evolved over millions of years, involve all kinds of subtle communications when we talk in person. Even merely talking over the phone (by voice) provides subtle clues which are not present in internet conversations. Whereas, on the internet we have a conversation between disembodied minds. Don't get me wrong, it's a wonderful technology, but it's missing a lot of color, the sense of the other person as a person, the embodied almost-sacramental aspects of human relationships.
Hence the email convention of including a smiley to say when we are joking. :-) (That wasn't a joke, that was just an example of a smiley.) Although, that doesn't always work either. As my father St. Larry once said:
You know how people are sometimes rude on Usenet or on a mailing list. Sometimes they'll write something that can only be taken as a deadly insult, and then they have the unmitigated gall to put a smiley face on it, as if that makes it all right.
This helps explain why you should avoid quarrelling with somebody by email. It seldom brings disputing parties into agreement. Emotionally tense situations are best resolved in more personable settings, if you can handle it. (Though sometimes email or a physical letter can be useful to broach a sensitive topic if you're too chicken to initiate the exchange in person. But that's different from quarrelling.)
So on the one hand, arguing with somebody face-to-face can trigger an unpleasant sense of Conflict! Conflict! with an accompanying adrenaline surge. It's annoying if your body starts trembling with fear when your mind just wanted to have a nice friendly conversation about how somebody else is wrong about politics or something. On the other hand, we instinctively know this and most of us adapt in order to be more personable and friendly when there's an actual face on the other end. It's much easier to see what's going on and correct it mid-stream. This leads to a 3rd point:
3) Long comments with a delay in responding. If I speak to you in person, then if I put my foot in it and begin to misunderstand you, or say something insulting, you will immediately respond and I have the ability to self-correct before anything goes too terribly wrong.
But if I'm in an argument on the Internet, that's not how things work. Suppose you read a long response from somebody and you start obsessing about in what ways it is wrong and needs correction. So then you write a long response of your own, but it's pretty easy to get carried away. If the tone is wrong, it won't be corrected until several hours or days later when an equally strongly worded message comes back, and that of course will itself generally be a disproportionate response (for the same reason) which triggers a similar reaction.
Of course, the whole thing can be nipped in the bud if both parties make a conscious effort to be unusually polite and respectful, but it's surprising just how much greater an effort it takes.
But even if the discussion is totally polite, there's a downside for philosophy. Long-winded comments make it too easy to talk at cross purposes, without correction from the other point of view. After all, when I'm writing a long argument I'm putting myself into the brain state where I am right and the other person is wrong, and one stays there for quite some time. This is dangerous to one's sense of balance and fairness.
Psychological studies have shown that when people hear evidence that their own strongly-held political views are wrong, the usual response is to argue against the new evidence. Paradoxically, this causes them to become more certain of their previous point of view [too lazy to find a link right now, but I promise I'm not just making this up].
From this perspective, arguments are rather dangerous things! Simply by expressing an argument for X, one naturally causes somebody on the other side to compensate by arguing for ~X. But this puts them in the position of a lawyer trying to make the best case for one side, not a judge disinterestedly weighing the evidence for and against. And as we all know, lawyers have a tendency to come to believe that their own side is right (even if it was basically a coin-toss which side they would be assigned to in the first place.)
This is something I worry about quite a bit as somebody who enjoys arguing about religion on my blog (and in person). Rational people should settle disputes rationally, but what if providing rational arguments don't tend to actually cause this to happen? What does one do instead?
One could compensate for this by asking people to argue for the other side of the debate for a change (one implementation of this is the Ideological Turing Test, adapted to religious arguments by St. Leah Libresco.) But this only works if we presuppose a strong interest in finding the truth. The "debate team" mentality where the goal is to win by coming up with sophistical bogus arguments, is not really improved by the fact that the positions are assigned randomly. That just makes it even more relativistic.
To try to get around some of these issues, the Socratic method of dialogue requires that the participants ask each other questions instead of arguing directly, and respond by making short speeches, not long. The other rule is that you can take things back as needed without any shame, instead of getting stuck defending one's initial reaction to the question. As St. Socrates says to Polus in St. Plato's Gorgias:
SOCRATES: Illustrious Polus, the reason why we provide ourselves with friends and children is, that when we get old and stumble, a younger generation may be at hand to set us on our legs again in our words and in our actions: and now, if I and Gorgias are stumbling, here are you who should raise us up; and I for my part engage to retract any error into which you may think that I have fallen-upon one condition:
POLUS: What condition?
SOCRATES: That you contract, Polus, the prolixity of speech in which you indulged at first.
POLUS: What! do you mean that I may not use as many words as I please?
SOCRATES: Only to think, my friend, that having come on a visit to Athens, which is the most free-spoken state in Hellas, you when you got there, and you alone, should be deprived of the power of speech—that would be hard indeed. But then consider my case:—shall not I be very hardly used, if, when you are making a long oration, and refusing to answer what you are asked, I am compelled to stay and listen to you, and may not go away? I say rather, if you have a real interest in the argument, or, to repeat my former expression, have any desire to set it on its legs, take back any statement which you please; and in your turn ask and answer, like myself and Gorgias—refute and be refuted.
So I guess the really philosophical way to argue on the Internet is chat! Text chats (IM) are still disembodied, but they have a much quicker turn-around time, perfect for Socratic dialogue. I use gmail chat all the time to talk physics with my physics collaborators, but I don't usually have philosophical discussions that way. But maybe I should.