You make your own rules as you use it, and you need to remember that everyone else is making their own rules as well. People are different, and the net can and will expand these differences. The 'bringing together' of diverse cultures rarely results in peace. That could be a lot of death threats on the Khomeini memorial web page. The posting continued for two or three pages.
People do say that sort of thing in real life.
Racism didn't start with the Internet. Where racial and ethnic divisions exist, we can't expect the Internet to magically heal them. Where such divisions exist, the Internet will bring together vast numbers of people who hate each other, and allow them to hate each other all the more. It will allow people with minority beliefs to join together no matter how far apart they are physically. People who thought they were alone will find others of similar mind on the net.