Start from several aspects: 1, propagate immoral ideas, such as self-mutilation, insulting people who don't believe in this religion and so on. 2. Encourage illegal crimes, such as hurting others and stealing. 3. Cruel persecution of pagans, such as the war between Christian extremists and Islamic extremists. 4. Anti-government and separatist ideas. It is most important to keep a kind heart. As long as you are single-minded, you won't do anything cruel, and there is no chance for religious extreme thoughts to penetrate. 6. If someone is found to spread religious extreme thoughts, you can call the police to stop the spread of such thoughts.