They'll get tired and look for someone else to play with. Each newsgroup is usually dedicated to a specific topic, or a general topic about a specific issue. For instance, airmail.general is a general discussion group about Internet America issues. You wouldn't post about gardening, for instance, in this group unless you were looking to get flamed. Take what you read with a grain of salt.
People tend to lose their civility behind a keyboard.
Just because it's in writing, doesn't necessarily mean it's true. Have a great time and be careful. News can be addicting.