They may even jump from abusing the original topic of the flames to abusing anyone who disagrees with them. Ignore people like this. If someone like this is constantly in your face, talk to our network people about it. Your news reader software can be set up with a kill file of people and topics to ignore. We can also block their e-mail and complain to the system administrators at their internet connection about their behavior.
Some flames are substantive arguments phrased rudely.
You didn't say it was an average. Choose your words more carefully. This probably won't impress a fanatical flamer, but it will tend to impress everyone else who reads the post. Some flamers will simply grow more and more abusive if you respond to them. A signature file is a file that your computer can automatically append to the end of an e-mail message or newsgroup posting.