The document proposes the idea of a website called Rivals4Ever that would create a single online platform for fans of rivals to express their support and opposition. It would allow users to create rivalries in different categories like sports, business, and technology, and equip fans with "weapons" to promote their side and attack the rival. The founder believes this idea could tap into people's passions on a global scale since rivalry is a universal human phenomenon, but no existing site brings both sides together in one place.