You may be familiar with some variant of this scenario:

You're on a mailing list (or web forum or Google group or whatever), where some topic you're interested in is being discussed. You see someone saying something you think is wrong. You fire off a quick reply telling them they're wrong, and move on to the next topic.

Later on, you get a reply, and for some reason they are upset at you telling them they're wrong, and you get upset at how rude they are, so you send another quick reply, putting them in their place. Who do they think they are, spouting off falsehoods and being rude about it.

The disagreement spirals and becomes hotter and more vicious each iteration. What common ground there was in the beginning is soon ruined by trenches, bomb craters, and barbed wire. Any bridges between the parties are on fire. There's no hope for peace.

This is called a flame war. It's not a good thing, but it's not uncommon in technical discussions on the Internet. Why does it happen and how can you avoid it?

As someone covered in scars of many a flame war, here are my observations (entirely unsubstantiated by sources):

• Flame wars happen because people try to be seen as being more correct than others, or to be seen to win a disagreement. This often happens online because the communication medium lacks emotional bandwidth. It is difficult to express subtle emotions and cues over a text-only channel, especially, or any one-way channel.

  Disagreements spiral away more rarely in person, because in-person communication contains a lot of unspoken parts, which signal things like someone being upset, before the thing blows up entirely. In text-only communication, one needs to express such cues more explicitly, and be careful when reading to spot the more subtle cues.

• In online discussions around free software there are also often no prior personal bonds between participants. Basically, they don't know each other. This makes it harder to understand each other.

• The hottest flame wars tend to happen in contexts where the participants have the least to lose.

Some advice (again, no sources):

• Try hard to understand the other parties in a disagreement. The technical term is empathy. You don't need to agree with them, but you need to try to understand why they say what they say and how they feel. As an example, I was once in a meeting where a co-worker arrived badly late, and the boss was quite angry. It was quickly spiralling into a real-life flame war, until someone pointed out that the boss was upset because he needed to get us developers do certain things, and people being late was making that harder to achieve, and at the same time the co-worker who was late was mourning his dog who'd been poorly for years and had recently committed suicide by forcing open a 6th floor window and jumping out.

• Try even harder to not express anger and other unconstructive feelings, especially by attacking the other parties. Instead of "you're wrong, and you're so stupid that the only reason you don't suffocate is because breathing is an autonomous action that doesn't require the brain, go jump into a frozen lake", say something like "I don't agree with you, and I'm upset about this discussion so I'm going to stop participating, at least for a while". And then don't participate further.

• Do express your emotions explicitly, if you think that'll mean others will understand you better.

• Try to find at least something constructive to say, and some common ground. Just because someone is wrong about what the colour of the bike shed should be, doesn't mean you have to disagree whether a bike shed is useful.

• Realise that shutting up doesn't mean you agree with the other parties in a disagreement, and it doesn't mean you "lose" the argument.

• Apply rule 6 vigorously: write angry responses if it helps you deal with your emotions, but don't send them. You can then spend the rest of you life being smug about how badly other people have been humiliated and shown to be wrong.

Your homework for this week, should you choose to accept it, is to find an old flame war and read through it and see where the participants could've said something different and defuse the situation. You get bonus points if it's one which you've participated in yourself.