While it's a sign of bad manners to start arguments, that doesn't mean that you can't disagree with people on Usenet newsgroups. If you want to debate an issue, please do. But don't get nasty. If someone flames you, ignore it. There are some newsgroups devoted to flaming, such as alt.flame.
Flames are usually very easy to distinguish from constructive posts.
LIKE THIS only serves to make you look like you're shouting. A flame will make reference to your intellect, your social status, your credibility, and possibly your parentage. Some flames are more subtle, and in a heated discussion it can be difficult to distinguish the real comments from the insults. Try to stick to the topic, and try not to overreact. Active debate and discussion can be a wonderful thing, but people often get carried away.