People do not understand the difference between a discussion, an argument, and a fight. You can see this by how often the words are used interchangeably. In actuality, they are very different things, and the more people that know the difference, the better.
A discussion is when people all talk about a single subject, either trying to understand it better or solve a problem. Discussions are non-biased. Everybody works toward the same goal, so if one person "wins", everybody wins.
An argument is when you make a claim and provide evidence to support it. You can argue for something or argue against it; in either case, you make a claim and support it. To argue with somebody is to have differing claims on a given subject. To describe arguing in one sentence, say "I disagree." Arguing should be civil. Just because you disagree with somebody doesn't mean that everything they say is wrong. It also doesn't mean that your beliefs are completely right.
"You are wrong and I am right. Now we're in a full-blown fight." Fighting is where too much discourse ends up. The reason is understandable. We get very emotionally invested in our ideas. They make sense of the world in a way that has proven itself consistent. Ideas very easily become beliefs, and that is when they get dangerous. Beliefs become a part of our personal identity. If you believe something, then it is true. If it wasn't true, you wouldn't believe it. So now, when somebody disagrees with your idea, it feels like a personal attack against you.
People need to know that they can have thoughts or ideas and care about them, but still be able to talk about them impersonally. Being passionate about something is fine, but there's no need to be rude. If you truly believe that your ideas are correct, then they will stand up to all scrutiny. So let people poke and prod and ask questions. If you can rationally explain why you are right, then be happy that you know the truth and that others learned. But if somebody has valid points when arguing against your beliefs, then be able to accept it and modify your beliefs. Again, in a discussion, when one person wins, everybody wins.