People argue and fight each other because they are intolerant of the views of others. Argument is caused by differences in opinions or perceptions. But most people always want to impose their opinions or perceptions on others. They wouldn't want to listen to the other person's opinion regardless of how valid such an opinion may seem. This is one of the reasons why some arguments lead to violence.
Everyone has a view point, even if you think the that the person's opinion is wrong, try to tell him or her calmly why you think such opinion is wrong without raising your voice or trying to make the person look stupid. Most people form their opinions about life's events from their experiences. So you have to reason with them calmly and in a responsible manner if you want them to listen to you and not be defensive.